What distro do you use at work? Using that at home would benefit you professionally as well. I’d start there unless it’s redhat.

I’m a beginner Linux user, without background in informatics, but after trying many distro, Ubuntu, Ark, Manjaro… the easiest to maintain and work as needed is Debian for me.

I thought you were describing Debian (FOSS only, stable and conservative, boring in the good way). It does take longer to get the updates because they build everything themselves, but that’s part of the stability deal.

I’m no expert though; I’m mostly reading to get suggestions for when I make switch properly myself.

Arch is best for you. As you have experience with Linux, you won’t have issues configuring it according to your needs. Arch wiki is a gold mine.

“highly configurable” and “very little effort to start using” don’t blend together in car mechanics, and they don’t in Linux either.

I was going to suggest Gentoo or Arch because they’re the standard for “highly configurable” but they really demand some effort to start using them.

Also, so far, only Debian really, really, cares about open source, most distros don’t mind copyrighted video codecs or proprietary GPU drivers if they make the user’s life easier.

If you’re ready to take a bit of a dive, take a look at NixOS. As a CI/CD guy it might be right up your alley.
It allows you to configure your entire system via a single, declarative config file, including any configurations for installed software. You could even develop the config in a VM and, once you’re happy with it, use the same for to configure your host machine.
Be warned, though: the wiki is nowhere near as good as the Arch wiki.

Help me choose a distro, please!

This is asking for trouble.

“Gentlemen, I am new to the country, and I was hoping that you could help me choose a political party.”

“I’m looking for a good text editor. What’s the best text editor to use?”

“I’ve heard that various religions have a lot of things going for them. Which religion do you suggest I join?”

Aside from very specialized distros (like, you probably don’t want Alpine Linux) most distros will work fine for what you want.

I use this machine for typical home usage: Firefox, a notes app (currently Notesnook), maybe office style tools like word and excel.

Firefox will run on everything. You can definitely take notes on anything, and there are tons of options. LibreOffice will be available for everything.

Steam,

Steam ships with its own set of libraries based on Ubuntu, and stuff targeting Steam will normally use them. It should be pretty distro-agnostic.

Discord

They apparently have a Linux app, which I’ve never used. The website should work fine anywhere. They have a “deb” or “tar.gz” and don’t specify any target distro for either. The deb probably is for Ubuntu, just because it’s the most-widely-used desktop distro that uses Debian packages, but I imagine that you’ve got good odds of it working on whatever. If you want to check, you could just throw a distro on a VM.

I don’t want it to ship with loads of applications; I want to choose and install all of the higher level tools. Shipping with a configured desktop is perfectly fine but not required. Ideally, I can have all of this while still keeping the maintenance low. I think that means a stable OS, a good package manager, stable/automatic updates, etc.

Everything outside of really specialized, oddball distros has package management.

All the major distros that I’ve used have options to do various forms of a stripped-down install. If you want to install a distro without anything graphical at all, you probably can.

You do have a differing release cycle; I’d probably tend towards a shorter one for desktop use. If you were setting up a ci server that you want minimal interaction with, you probably don’t care much about having newer software. But, again, distros tend to have at least options for a LTS release that just gets security updates, even if they have a pretty-frequent set of updates, like Ubuntu.

There aren’t going to be particularly “unstable” distros in the sense of crashing. Debian stable is aimed at being software that’s passed through multiple phases of experimental testing use and is considered well-tested; it’s just their normal distro. There’s no pixie dust that makes some distros less-crash-prone. If you’re really determined to have more testing, you can use an LTS release, which many distros do but I would not advise for a desktop, especially if you’re planning on playing commercial games, which you say you are.

Last bit. Open source is rather important to me. I prefer free and free.

You can get open-source software on any distro. Debian is a bit more aggressive than some, turns off non-free repositories by default, but I think that most people turn them on anyway. They also have a separate non-free firmware repository, and I think that most people aren’t determined enough to refuse to use non-libre firmware for hardware that they have (though they might choose that hardware with libre firmware in mind). I don’t think that there’s any distro that is going to ram non-open-source stuff down your throat. Honestly, your largest source of non-open-source software is probably going to be Steam, which you said that you want to use.

I use Debian myself these days. I’m hesitant to argue in favor of distros, because my own take is that the differences (a) tend to change over time, (b) most work pretty well regardless, and (c) I think that few people have actually spent enough time on many other distros to be able to have expert knowledge in their failings (which is something that I’ve seen in vi-vs-emacs discussions, where I’ve seen enthusiasts often talk about amazing features while unaware that the other editor can also do the same thing; it takes decades to master either).

If I were picking a “first distro” for someone for desktop use, and disregarding your specific situation, my default is probably Ubuntu. I don’t use it myself these days, but it’s particularly-widely-used. It has a short release cycle on the non-LTS version (I know that you said you wanted low maintenance, but I’ve pretty consistently found that one winds up wanting to pull in newer software for desktop systems). It’s Debian-based. If one distro gets targeted by a proprietary software package (which I know you also said that you don’t care about) it’s probably going to be Ubuntu. Aside from past use of Upstart as an init system, it isn’t especially unusual. It doesn’t require some of the poking around (like enabling non-free repos) that Debian does. It may or may not be where someone wants to be long term, but it’s not going to bring a lot of complications. But it’s really not going to be drastically better than the other mainstream distros.

Whether that is what one chooses or not, I’d stick to one of the more mainstream distros for a first-time user. There are legitimate reasons to use oddball, young, and specialized distros (tiny, security-hardened, real-time oriented, scientific-computing oriented, music-production oriented) but many of them die out after a couple years or impose constraints that aren’t immediately apparent to a new user.

I’d suggest something that’s been around for at least ten, preferably fifteen years. A distro that’s accomplished that has enough of a track record that they aren’t just going to be a flash in the pan; they’ve been able to attract and maintain enough effort to keep up an ongoing release cycle, which is not easy and I think is often more effort than would-be distro maintainers realize. Most distros that have come out since I started using Linux in the 1990s have died off. If yours gets discontinued, then you gotta migrate off it, which is a pain. But again, if you choose something new and it never sees another release, migrating off it isn’t that bad. You’re gonna maybe have to learn a new package manager and some new ways of configuring things and new conventions, but most distros don’t vary that incredibly much.

I like Fedora and PopOS. I find PopOS to be the most exciting and best out of the box experience, with plenty of options for customization. Endeavour is also fantastic and considering you have lots of experience with Linux already, should be and excellent choice as well. If you want kind of a set it and forget, I can’t recommend PopOS enough. Fedora for if you want to tinker and set things up to suit yourself more, and endeavour even more so.

Linux Mint

So its not really a distro, but what i do on my laptop is installed rocky 9 linux and use distrobox for installing applications. Rocky is Based on Rhel, its lts is good till 2039 and is super stable

If you’re fine with rolling release distros, go for EndeavourOS. It’s based on Arch (uses the Arch repos as well as its own for its specific needs) but has everything configured for a working desktop out of the box. There’s not much I can say that everyone else hasn’t, if you like the Arch ecosystem but don’t like the (potential) tedium of setting it up, EndeavourOS is good. The thing with rolling release distros is that the package release cycle is not stable. This is not to be confused with reliability, Arch can be a reliable distro, but where most distros stay on a particular version for its release cycle, a rolling release distro updates its packages as soon as the new version comes out. If you want that, then go full steam ahead on Endeavour.

I’m gonna throw another distro for you to try, if you’re not a fan of the nature of rolling release: Nobara. You mention you wanted something stable with a good package manager, and IMO Nobara fits the bill. Like how EndeavourOS is based on Arch, Nobara is a gaming-oriented distro based on Fedora, which updates every six months. The guy who runs it works/worked for Red Hat and is responsible for the GE-Proton patches that help extend Steam Play compatibility unofficially, and he wanted to make something that was as easy as switching a game console on. There are a lot of patches and tweaks done to the kernel and apps as needed, to ensure that the user doesn’t need to reach for the terminal as often, if at all. You can still do your productive work on Nobara, you can just think of it as Fedora (an already solid workstation distro) but with a gaming flair to it.

TL;DR: For stable releases, get Nobara. For rolling releases, get EndeavourOS. If one pisses you off in the future, go for the other lol

I’d recommend Fedora, but the suggestion of EndeavorOS is also good.

I recommend Linux Mint. It comes with good default settings but is configurable. The Cinnamon DE is exactly like that of Windows, so you don’t need a lot of effort to start using it. Mint comes with some pre-installed apps like Firefox and LibreOffice, but they may not be the latest versions, so you can purge them afterwards and reinstall through one of the package managers.

Speaking of which, Mint comes with APT and Flatpak as package managers, but Snap is disabled by default. You can enable it, if you want to.

Mint does not come with any gaming apps pre-installed, but Steam can be installed, and many games work on it, especially those that are verified to work on the Steam Deck. Lutris is another game app you can install, and that allows you access to other game platforms like Blizzard, but don’t assume that all games will work perfectly through Lutris.

Distro Chooser is giving you great advice. I love EndeavourOS. First started out on it with KDE, now I’m on sway, everything just works perfectly, so I can definitely recommend it!