So I'm using a Mac but my gaming rig is still running (cracked) Win7 and steam is about to stop working on it in few months and I was wondering to which OS I should move to? I'd be interested in trying Ubuntu but I'm not sure how gaming is on Linux. What's the least shitty OS I should go to? I'm basically using it to play DayZ, Cities skylines and AoE2 few times a month.
Ubuntu should be fine especially given GNOME clearly borrows some visual concepts from OSX. I prefer Linux Mint myself, but that uses Ubuntu as a base so I'm not exactly blazing a brave trail. Most games I have work. Unless some anti-cheat is involved that the dev does not support Linux with you will most likely be OK. Baulder Gate 3 works excellent and that has sucked up most of my time. Join the ranks. Pump up the valve hardware survey Linux numbers. Make the business people in control of the devs care about linux support somewhat. Free yourself form the whims of Microsoft.
At the risk of a distro fight, if you bounce off Ubuntu give another distro a shot. I can't really explain it but I had issues with Ubuntu being almost to streamlined; it mostly worked out of the box as advertised but when it didn't I had no idea what was going on.
I just learned more quickly on Debian. It's a personal thing, so it might be you as well.
I'll also add: if you're new to Linux you're used to thinking about the Explorer, the desktop environment, etc as part the OS. They aren't. With nearly every Linux distro, you can have a more Mac like desktop (gnome) or windows (kinda KDE Plasma). And in either of those if you don't like the file Explorer there are options there to.
Most of what Ubuntu does stock should be fine, but I just remember getting used to things was easier for me with plasma than gnome coming from a windows machine.
edit: I wanted to add, some people have strong opinions about which of those other elements are better (desktop environments/explorers). It's mostly taste, except when it isn't, because they do in-fact have aspects than can be important. Stick to something well known and used while starting.
AoE2 works on linux and DayZ should also work with some minor fiddling (according to protondb), cities skylines is native to no problem there. You should stick with ubuntu if you are unfamiliar with linux.
I used Linux for a while many years ago, and I just switched over again the other day after the Windows updated and brought the search bar back (yes, this is the dumb thing to push me over the edge). I'm using a flavor of Ubuntu, and it's amazing so far. It's so much better than I remember. Managing software updates is easier, customization is fantastic, and I'm pretty sure it's more responsive.
I can say GamePass doesn't work on Linux, which is a bummer, but most Steam games should. I've only played Factorio so far, and it ran fine. Since Valve launched the Steam Deck, a huge portion of the Steam library now supports Linux. It shouldn't be too much of an issue for you. Dual boot and give it a go. It's free and takes very little effort.
Steam Deck and by extension Proton being heavily funded by Valve mean that Linux is a seriously viable gaming setup now. I can play pretty much every game I want to play on Arch Linux now. Even games that don't support it (NB: you need to enable use of Proton in the Steam client).
You can check here for games that will run on Linux to make sure your 'must haves' are supported: https://www.protondb.com
Personally I've been playing Apmplitudes games (even pirated ones [Humankind, Endless Space, Endless Legends]), Cities Skylines, HOI4, Stellaris, Dead by Daylight, etc.
I've actually found a few games (Paradox esp.) run better on Linux (using Proton) than they do on Windows.
Running on Fedora right now. Given that it's not the best distro for gaming, it's still very decent IMO with my choice of hardware (1st gen Ryzen and Vega 54). Even Halo and Forza 5 are running pretty well.