What is some good FOSS software for recording/producing music?

Ardour. Fun fact, it's primarily developed by Paul Davis who was one of like two other people in the garage with Bezos working on building Amazon at the start. He took that windfall and just used it to retire and work on FOSS passion projects the rest of his life.

For a recording computer, the very first thing you're going to want is a low-latency audio interface you can plug microphones into. These don't have to be terribly expensive, but you don't want to go too cheap. My favorite bang-for-the-buck interfaces are the Behringer UMC204HD or UMC22, but if you think you might need technical support better go with something like a Focusrite Scarlett.

Then, you need software that can use the low-latency ASIO drivers for the interface, which Audacity can't unless you build it yourself from source code. The reason you want low latency is that it lets you listen to what you're recording actually sounds like as you're recording it, without a distracting delay between the sound in the real world and the sound in your headphones.

So, you need a DAW. Ardour is open source but it isn't free on Windows; Reaper is a better choice, even though it isn't open source. No DAW at any price is better than Reaper for tracking live instruments. It's widely used in professional contexts. It's also wicked fast, and the tutorial videos on YouTube are fantastic (Reaper Mania channel) and well-organized in practical use cases.

The main "drawback" with Reaper is that its built-in mixing effects prioritize functionality and power over appearance; you kinda have to know what each slider and knob is supposed to do (or look it up), and there aren't a ton of presets to fall back on, even though everything you need is actually in there. It also doesn't come with loop packs or software instruments like digital synths or sampled pianos etc. like more expensive DAWs do. But resist the urge to solve these "drawbacks" with money - there are tons of free and/or open source plugins and software instruments out there for the searching - look at Decent Sampler / Pianobook and Spitfire Labs for instruments, ReaPack for community-built Reaper extensions (especially the Tukan stuff), Kilohearts and Melda for excellent free utility plugin bundles (that duplicate things Reaper can already do, for the most part, but with friendlier interfaces).

Audacity is an excellent recording program.

Hydrogen is an excellent drum machine.

There is a free software DAW named Ardour which seems pretty complex, but I don't do enough audio production to compare it against commercial alternatives.

LMMS is also pretty cool.

Then there's always MilkyTracker if you want to go medieval.

IMO, where FOSS audio production shines is not in any specific DAW software, but in the capabilities offered by toolkits like Jack and PipeWire to take audio and MIDI outputs of any program and plug them into the inputs of any other program. The ability to run commercial VST plugins in WINE is a bonus.

There are dozens of arbitrary synthesizers and sequencers out there, all with unique perks and rough edges. But there is strong infrastructure to create a pipeline from all of these individual components. You are required to fuck around with it.

You want Reaper over audacity. (Even though iirc it is proprietary).

There is a FOSS true DAW on Linux I tried once. It was decent on its own, but plugin support was ass.

Audacity is the actually FOSS answer, afaik. I've used it a lot, but not for music (much). It's not a DAW, but if it's just recording and stitching tracks together it will 100% work, and with some effort you can do fancier stuff.

There's also Ardour and Zrythm which are more real DAWs Ithink? but I know nothing about them. Maybe try ardour if you already know you don't want to do audacity

Reaper!

Also, not open source, but Cakewalk is free nowadays.

I just like to record myself playing the guitar once in a while and use Ardour with my UMC 22 audio interface. For me it is just great.. I can record my voice and guitar, use some plugins to get a better sound out of my cheap guitar and mic.. and record different tracks and sync them. I'd recommend Ardour and the behringer audio interface all the way.