If you have to pick only one Desktop Environment and use it till your computer breaks, what would you choose?

KDE, always
Used it since I switched to the Linux Desktop 25 years ago. Quickly tried gnome, and others, and hated it.
KDE is fast, efficient, looks awesome, is ready to work with, and highly customizable

KDE plasma. Coming from 30 years of running exclusively windows it's just the most comfortable and easy for me to use (way more than Gnome). Easily configurable, works. Can't ask for more.

KDE plasma, unless it's on a tablet, then Gnome

KDE Plasma for ease of use if using Nvidia Otherwise Hyprland or exwm

MATE has been on most of my machines, except the BSD ones.
But past year or so, I have grown a fondness towards ctwm, and gradually migrated my machines to it, Linux and BSD alike.
It is not a DE, but the fact that I have to assemble my suite of software myself on my machines, makes the point of using DEs moot.

I'm a long time supporter of Xfce, but I have to say Cinnamon these days. It's light on resources while being feature rich. Also it's the default on Mint and it just works.
- I use XFCE, but I like Cinnamon too. I use Nemo and Xed instead of Thunar and...whatever.

Cinnamon for 2 reasons
KDE is missing a lot of features which still only works in Gnome. Like the taskbar Calendar app syncing events with services like Google Calendar
cinnamon is extremely stable and doesn’t move your icons around when you connect to an external display with your laptop and the display has a different resolution.

Probably KDE, it's the most 'complete' feeling to me with settings and GUI for most things.
- I would say the same & I don’t even use it—but I would trust it being around the longest & is better than GNOME IMO.

Switched from i3 to sway to hyland. I like the virtual desktop setup and noiseless facing interaction.

KDE for the desktop and xfce for the laptop
- why not kde for laptop?
  
  I'd imagine lower power laptop? Though I'm using KDE on a laptop from 2012 and it works fine

i3
best tiling on X
- I am absolutely with you about i3. Simply great (there is also dwm or qtile)! But it is a WM, not a DE, what OP asked about.
  
  fair
  xfce+i3 i guess

KDE the customization is off the charts

KDE. Been upgrading the same environment for 5 years just keeps getting better.
I started around maybe KDE 3?
- Was on KDE 2, KDE 3 was absolutely incredible, ran it on Mac when it was supported on xquartz.
  4 was a mess, but got better, 5 & 6 are fine, but it's overall far better than any other DE, it's just so customizable, the only other thing that comes close is xmonad or something.

Probably Plasma because it's familiar and you're able to customize it extensively over time.

KDE for sure. The modern versions look exactly like how I want a desktop environment to look out of the box, and they keep the full range of customizability that a desktop should, IMO, allow it's users to have. Which is something Windows just kept slowly getting rid of over the years.
I also prefer to have a taskbar that is ever present with a traditional start menu that's cleanly organized by category rather than the current full screen pop up "activities" search thing gnome does nowadays.

XFCE would be my choice too

True people only use i3 or the-other-i3-for-wayland
/s, of course. But still my personal choice

This isn't even hard. KDE without a second thought.
I regularly try other desktops, and I regularly come back to the only desktop with any sort of reasonable thought put into it.

Xfce

I'm a cog in the machine and use KDE, but xfce is awesome, I would use xfce if I couldn't use KDE.

The amount of not KDE answers here surprises me. Y'all a bunch of nerds [endearing]

That's not too hard a question for me, I've been using the same DE for years: KDE
- KDE is one of the main reasons for me to use Linux. I immensely like the performance, silence and battery lifetime of MacBooks. But if I have to work with anything but KDE, it's not worth it for me. The only thing OSX does better than basically any other desktop out there, is the ability to drag whole virtual screen between monitors.
  
  I'm running XFCE (but you could do KDE) on my intel Mac, you can get best of both worlds. I heard silicon is more difficult with Linux tho.
- Has KDE improved since 2010-ish? I gave up KDE because gnome was just a better DE at the time. Gnome sucks now, but I found i3/sway. Haven’t given KDE a second chance yet
  
  Oh yes. Much better since the KDE4 branch / debacle.

I keep coming back to KDE time and time again. It's so easy to mess with, I can set it up exactly how I like it without much effort, and it always looks good because someone else did all the work making themes and widgets I use.
That said, I love XFCE, I'm just trash with CSS so it takes me forever to get it how I like, and on my Surface I can't get the scaling to work so everything is beyond tiny.

Definitely Gnome here. Though I have a long list of notes, it mostly just works exactly like I expect with little friction or guessing. I donate $100/year to both Gnome and KDE since they are both good pieces of software, and I love that I get to chose mine. Further, I think KDE is the logical choice for something like the SteamDeck where it's going to have a lot of gamers that expect computers to work like Windows. (even if I don't like it, >_<)

I'm happy with Linux Mint so far (2 mos in)
- which desktop env tho? Cinnamon?
  
  Yes, Mint Cinnamon. Weird combination of names tho, I don't even want to think about combining those flavors.

Sway for a laptop, Plasma for desktop.
Had you have asked me a few weeks ago, I probably would have said Sway for both,.or maybe Gnome for the desktop... But I decided to check out KDE again for the first time in like 20 years, and while it's still kind of a hot mess it has come a long way.

Always wanted to like gnome but never could, and xfce is fine but I much prefer KDE, it is verry likely that I'll actually keep it till my pc breaks.
- That's the beauty of gnome: they don't give a single fuck if you like it. You can return the favor.
  
  Gnome has the apple philosophy that the user conforms to technology, not the other way around.

KDE.

I've been using Mate ever since Gnome-2 transitioned to Gnome-3 and I didn't like the transition. I like a clean screen with simple menus, Plasma is just way too cluttered for me.

There is nothing better than Xfce, if you dont like the desktop, at least Xfce allows you to customize. KDE seems interesting, but the last time i tried it, 10 years ago more or less, it was a bit buggy.
- You owe KDE a second look if it's been that long.
- I remember when kde looked like xfce and yeah back then it was buggy. Today it looks like a slightly jank windows 7 but with the giant buttons and curved corners that characterize 2015 software.
  Most of the bugs seem to come from Wayland still being vaguely trashy and kde not having fully migrated from xorg

Gnome.

Cinnamon by and far.
I've used so many distros and DEs I don't even know where to begin, but Cinnamon got me hooked for the long run. It's legitimately the most polished and "ready to run" DE I've ever used, yet still allowing for far more customization than Windows ever offered.
- Cinnamon's been working well for me; I'd choose that, and I don't mind waiting till my laptop breaks to reassess what DE I want!

KDE

KDE Plasma.
It has been great for gaming, adopting Wayland protocols at a faster rate than other DEs due in part thanks to Valve's contributions.
I freaking love GNOME & Adwaita, but I'll switch back when I deem it better than Plasma.

GNOME because it works out of the box like GNOME

I'd say Gnome, since I'm so used to it that I feel it doesn't get in the way of the things I'm doing.
Because that would be my aim: something that doesn't interfere with the work I am doing.

Plasma, been using it since I was a kid
- Plasma's not that old, it just came out a few years ago...
  2008?
  
  K so I just realized they didn't call it plasma until 2008, I first used KDE in 2005.

I'd rather not use a computer at all than use GNOME for the rest of my live.
For me it's KDE Plasma all the way.
- It’s wild to me how GNOME evokes such strong opinions in folks. It really is a love it or hate it kind of deal (I’m in the “love it” camp).
  I wonder why that is. I like KDE ok, but it doesn’t elicit a strong emotion from me. KDE works fine, I just really like GNOME.
  There must be something about GNOME in particular that some people love, and others hate.
  
  For those of us that expect room to breathe and make our machine work for us rather than the other way around, we feel like Gnome takes a lot of liberties away for the sake of "simplicity." There is so much missing from Gnome that is present in most other DEs and even custom WM setups.
  The primary contributors who work under The Gnome Foundation also come off as controlling and arrogant in a lot of cases, and refuse to take community feedback to heart, whereas KDE has literal summits to get user feedback on major core features we want to see which then later get added to their backlogs and sprints as Epics. Gnome acts a lot like Apple in the sense that they're very much "we know what's best for you better than you do."
  Now, the singular area I can give Gnome true props in is their accessibility functionality, but that's primarily it. KDE's accessibility is fairly behind by about a decade in comparison.
  That's just my take, take it as you will.
  
  Honestly, that defaulting to the Search field in the Save dialog when I'm trying to save something just gets me wild. It beggars the imagination why the developers think that's a reasonable thing to do and it colors my whole perception of the DE.
  
  There must be something about GNOME in particular that some people love, and others hate.
  GNOME is heavily opinionated.
  As such it gets praise from people that share that opinion and gets hate from the people that do not. Many other DEs are much more configurable, giving a broader audience the possibility to adjust everything to their liking.
  
  You know how the ending of LOST or Game of Thrones can bring up feelings in people? That's how it was for me when Gnome 3 first came out. I had been using Gnome 2 for a few years and had a good workflow, and then suddenly, everything changed. Back then Gnome 3 was buggy and lacked a lot of things, which didn't help. It also didn't help that the devs took a "the problem is you" stance to all feedback. That said, I use Gnome now, and I like it, it took some years to mature and become good. But the feeling is still there sometimes.
  
  GNOME is a lightly upgraded MacOS interface. Every time I’ve had to use a Mac has pissed me off so GNOME gives me war flashbacks.
  Not necessarily the DE’s fault but ¯(ツ)_/¯
  
  I was team Gnome before Gnome 3 came out. Nowadays I don't mind it for auxiliary computers that I don't interact with regularly. It has a huge community behind it and that is a quality in its own right. But since MATE never really managed to become a worthy successor to Gnome 2 I guess I'm team Plasma now. I got it "forced" on me by my beloved Steam Deck and I can definitely see why Valve went for it.
  Currently I'm experimenting with Hyprland but that is definitely too early to call it my forever pick, so Plasma it is.
- why do you think gnome is the default on everything?
  
  Because distros have a sick sense of humour.

My computer doesn't really break, I'm Ship of Theseus-ing it regularly.
Apart from that, the only one among the normal window based ones that has felt like it respects my will to configure stuff in ways that feel right to me has been KDE Plasma.

Desktop environment? Who needs a desktop environment?
- Bro watches videos through ASCII conversion in the cli😭
  
  TBH, I've always wanted to do this.
  
  mpv for the win
  but if you really want your ASCII conversion: mpv --vo=caca or mpv --vo=tct
  
  Bro doesn't need DE to watch videos. Bro doesn't need DE to do anything.
  
  Bad apple in text may be more impressive than it on the Nintendo.

KDE Plasma, I can't go back to SDR

I thought KDE was the popular choice to be honest. I feel like all the toolp newish OS are using KDE and the top old OS are using Gnome.

Until my laptop dies or cannot support it, I'm sticking with KDE Plasma. Love how MX configured it (because I'm lazy) and absolutely will keep using it for as long as my laptop survived or can hold it.
Might try other ones in VMs (like ratpoison) in the future for other machines I might set up in the future, but for now KDE Plasma is my go-to that I'll probably be using for a long time.

Herbstluftwm with dmenu. Just a windows manager. I've gotten used to using the command line for things I used to rely on a DE for.

KDE

XFCE. It's lightweight, easy to tweak and looks great. I run it on my 6 y.o. potato laptop
- The surprising thing is that KDE would run on there just fine too. If you don't add all the PIM stuff, it's almost a wash in memory usage and just as snappy.

gnome head all the way!!!

Xfce, ol' reliable.

XFCE, using it for over 10 years, not planning to change it unless the DE changes radically.

LXQT or KDE I just like the QT look and feel.
GNOME is great in general but not for me, it is too much MacOS alike and too limited for my liking.

KDE - I love to tinker and own my DE. 😎

any computer I need to be stable enough for work/school: KDE
any computer whose primary purpose is for goofing off and gaming: LXQt (and I will spend the entire time configuring LXQt instead of gaming...)
- Why not use steam or arch if it's just fucking around? Arch you can at least configure easily.
  
  tbh hadn't heard of steam and always assumed arch was difficult to learn. but i had been considering trying arch just to see what the hype was about

Had To scroll way too far to find Cinnamon so here's back to the top.

If it has to be a DE then I'd go with XFCE, otherwise I'd probably go with openbox.