You described EndeavourOS if you ask me. It's Arch but preconfigured, so ready to use after install while being as configurable as Arch if you want to go further. Has AUR so you won't have problems finding a program.

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Debian 12 with your favorite DE, I use XFCE

I can't recommend enough EndeavourOS. It has a very good defaults and its softwares is very up-to-date since it's based on Arch Linux. Their community is also very nice.

Of course you can try Arch Linux too, it's minimalistic and you have to configure most thing yourself. It's not really hard, but gonna take some time.

Fedora and Linux Mint is also a very good choice.

I recommend Linux Mint (21.2), which a based on Ubuntu (22.04) and Debian. The cinnamon desktop environment it comes with is pretty similar to windows 7, which makes it easier to use. I think 21.2 will remain supported until 2027 as LTS.

You might want to look at distrochooser.de. That said, Linux Mint and OpenSUSE are good, stable distros.

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

I'm going to ignore your "Planned Usage" section. Why? Because that's more-or-less about which software you install, not about the distro (well, not if you choose a well-enough maintained distro at least). If it was a question of family of OSes (windows, mac, linux, BSD) that might be different.

You want Debian, here's why:

I'd like an OS that’s highly configurable

That's most distros

but ships with good default settings

That's Debian. I installed it when i was still a newbie to computers in general, and it hasn't bit me in the ass yet.

and requires very little effort to start using.

See previous answer.

I don’t want it to ship with loads of applications; I want to choose and install all of the higher level tools.

My first Debian was a headless install on my laptop so I could customize the graphical stack. In hindsight, I wouldn't recommend going that barebones unless you actually do take advice and RTFM. I went without a compositor for several years, as an example of why.

Shipping with a configured desktop is perfectly fine but not required.

On the flipside, Debian has GNOME, Xfce, KDE Plasma, LXDE and MATE as installer options. You can also install any Desktop Environment that works on linux, as it is more higher-level software than OS-dependent software.

Ideally, I can have all of this while still keeping the maintenance low.

My other PC is also a Debian (need that on a bumper sticker). It's my daily driver desktop (the aforementioned headless install is a laptop); I set it up based on installer defaults and have not had to do any low-level maintenance on it for the past 2 years that I've had it.

I think that means a stable OS,

Debian is stable af. The downside is that they don't really have bleeding-edge software on the default Stable repository. Testing is newer, and still 99.9% stable, but also not the absolute newest. Unstable lives up to its name, I'm told, but haven't felt bold enough to experiment.

Really though, I'm going to guess that any fixed-release update cycle distro will be as stable as Debian, and any rolling release will be about squashing compatibility issues to make sure you can have bleeding edge software. There are some distros that strike a balance more in the middle of those two, so that's up to your preference and you should probably try out a few before you settle for what someone on the internet says is "The Best." (The main difference between the others and Unstable is that Unstable is a rolling release, instead of fixed)

a good package manager, stable/automatic updates, etc.

Apt is mostly a positive experience. As I mentioned, before, using thr Stable repository will ensure updates are stable and don't break compatibility. I have never had the Pacman experience of not being able to update because there are unresolvable conflicts; the few times I had issues, they were simple enough to fix with a dpkg --configure -a and/or apt --fix-broken install. It can be slow, but frontends like Nala have made that less of a dealbreaker for me.

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

Debian's core driving principal is FOSS. You definitely can still download and run non-free software on it, and there's even a small section of the main repository that includes non-free sofrware, but the primary guiding principles of the Debian repository are the Debian Free Software Guidelines. Note that these principles are more restrictive than the FSF's definition of Free Software, but the most part there is a large overlap.

Here's a link to the installation page, which includes links to various installers and the installation guide.

The wiki isn't as likely as Arch to come up in searches if you just search terms like "linux [software]" or "linux [issue]", but it's an invaluable resource, almost as thorough as Arch's, and the Debian Project's recommended way for ensuring accuracy to your system.

Finally: I'm going to do that annoying thing nerds online do and tell you that you asked the wrong questions, then answer the questions they claim you should have asked. The linux community as a whole supports and encourages experimentation. You'll find your journey more fulfilling as a whole if you go outside your comfort zone and try new things, do it differently instead of sticking to recommendations and what you know. I know this message is at odds with how much I've talked up Debian, but I was answering the questions you asked.

The truth is that your tools should suit you and your needs and your style of problem solving. All softwares, including the most basic parts of an OS, are tools and therefore benefit from trying different options. Do you want "eh this is okay enough to get the job done" or "this is a fun and fulfilling way to complete projects"?

When you install, whatever you install, partition your drive so that /home is it's own partition. Then if/when you reinstall, distrohop, whatever, you don't have to worry about copying over your data. Just use the same /home partition, and format the others. You can actually use this to try multiple distros at the same time - you can install them in different partitions, but have every install use the same /home partition. This is a nice way to test new distros without blowing away your stable install.

Now, for my distro recommendation - Ubuntu gets a lot of hate, but honestly, after 15+ years of Linux, and having tried Mint, Fedora, Arch, Manjaro, and many others, I always end up back on Ubuntu. It's easy, it's stable, and it stays out of my way.

The defaults are good, but you can customize as much as you want, and they offer a minimal install (as of 23.10, it is the default) which comes with very few applications, so you can start clean and choose all the applications you want.

Unless you are excited to tinker, I'd really recommend starting simple. Personality, I just want the OS to facilitate my other activities, and I otherwise want to forget about it. Ubuntu is pretty good for that.

Pop os or mint

I would recommend Arch and derivatives (supposedly EndeavourOS is Arch but better for beginners, I've never used it though) or NixOS, they're highly configurable & have good package managers.

I would not recommend debian or it's derivatives because apt package manager is way worse than pacman.

Also while Arch is a rolling release OS, it's not really unstable, it's not like it constantly breaks with updates.

I've used Linux Mint a bit at a relative's house so they can have an easier & more "stable" GUI experience, but there weren't all the packages I needed on the GUI software manager, and even some packages that existed didn't want to install until I used the terminal anyway.

And as I mentioned earlier apt is just a worse package manager than pacman so it's a pain to use.

Especially since I was using plain Bash without good tab completion unlike Fish or Zsh, which makes the much longer apt commands that much more annoying to type in compared to just -Syu -S -Ss -Qs -Rns.

And it's not just that the commands and package names are better and shorter on pacman compared to apt, but there's more packages (and I'm not even counting AUR).

For example, on Linux Mint I were going to install wine-mono and wine-gecko, which you're going to want if you plan to play windows games outside steam proton, but they didn't exist and I had to follow the https://wiki.winehq.org/Mono and https://wiki.winehq.org/Gecko installation guides instead of just downloading 2 binaries through pacman.

And tbh I eventually gave up on wine-mono and just got the .net runtimes I needed through winetricks.

If you're really supper worried and paranoid then instead of Arch you can use NixOS, it's whole shtick is that you can have multiple versions and always roll back to before anything broke.

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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.

Pop_OS!

Slackware. Read the official installation guide and see what you think. YOU are the package and dependency manager, but there are several helpful tools. Nothing goes on or off the machine without your direct intervention.

You will probably find the open source nouveau (nvidia) driver lacking for gaming on any distro. The proprietary drivers help. But if you're passionate about foss then you may want to trade the 3070 for an amd gpu. I swapped me 3060 ti for a 7800xt recently and have been very happy.