Linux

A Linux distribution is just the Linux kernel distributed with various other pieces of software that make it usable. Often times, there are multiple software projects that aim achieve the same goal by going in different paths. These are packaged together by the distro maintainers who mostly do this out of passion.

Different distros prioritize different aspects of the software they package and they do this in different ways. To make the best choice for you, it is best to try and understand what each distro aims to do. Here are a few examples out my head:

• Debian is a traditional distribution that aims to keep the system stable for a few years. They do backport security patches, but slow rollout of feature updates is a deal-breaker for some people (like me).
• CachyOS (based on Arch Linux) compiles it's packages utilizing newest CPU instructions which may lead to slight performance gain on newer hardware. They also ship some kernel patches optimizing it for gaming use cases.
• Bazzite is based on an atomic/immutable version of Fedora. The aim here is to provide a system that makes it very hard for users to mess it up, using containerization technologies. It also means that installing packages in the traditional way is not very feasible or recommended. You are supposed to install packages without root access and using technologies like flatpak. It also includes some gaming specific kernel patches similar to CachyOS, but not as many.

Grass is greener...Linux is a kernel with tools attached that distributions play with and present as they would as a distribution. Packaging (program management) is different throughout with all the distros loving their 'tool', or, methodology. Some distros present helpful scripts to get a thing done, or, look a way, or, whatever, and some do not.

Windows tells you, here, you can use this or do this and cannot do this or use that. Linux tells you to simply have at it and makes it all available for you to use or not to use. Windows sits you at the kiddie table whereas Linux gives you materials and tools.

The better comparison is that distros are the operating systems (like "windows", "macos", and "android"), while "linux" is the kernel under the hood that end users likely never interact with (like "NT", "XNU", and..."linux").

A distro represents an intended user experience. If you want a distro that has an intended user experience that is similar to windows, go with Mint or OpenSUSE. If your desired experience is like the SteamDeck, install bazzite (with an AMD GPU ideally). If that's all you care to know, then that's all you need to know; go use your new system how you would any other.

But if you want to dig deeper, yeah, the fact that all the distros are based on linux (and more importantly, are posix compatible) means that a lot of the software is portable across distros. But that doesn't mean your experience on all distros will be the same. Different distros organize their filesystems differently, they might ship with different versions of core utilities based on the stability testing they've done, and they likely offer varying means of installing and managing new packages.

The tl;dr is, go use one distro, and then later try doing the same stuff in a different distro, and inevitably at some point you'll go "oh, this didn't work exactly how I expected because the other distro I'm used to handles this differently". That's the difference.

First thing to consider is they all use the same Desktop Environments.

Unlike Windows, in Linux the "graphic" is completely separated from the operating system, any DE can be uses on any distro, so trying different distros that come with the same DE, might make you think there's very little difference (at first look).

Second, almost all distros are derivatives, that contributes to make them feel similar. The original ones are just a bunch: Debian, Red Hat, Slackware, SuSe, Arch, Gentoo, everything else is based either on one of those or on another derivative, if your curious you can have a look at this graph: https://en.wikipedia.org/wiki/File:Linux_Distribution_Timeline.svg.
So for example, if you take Ubuntu and Mint, they might look similar because Mint is based on Ubuntu.

If you want to see the real differences, you need to look at the original ones, the core differences are: the way software is packaged and managed, and the "philosophy" behind the way the system is overall administered, maintained and released.

Derivatives add differences to the user experience, they main reason they're created is someone is not completely happy with the way a distro does things and they create one the meets their needs, for example, Debian is improved dramatically on the user experience lately, but many years ago was quite arduous to setup and use for non-experts, so Ubuntu was born.

Now to answer you question

as long as I choose one that gets regular updates, it doesn’t matter fundamentally?

It does matter, tho it's not as much world-changing as some people seem to think (especially when it comes to gaming).

The most important things are support for your hardware and easy of administration/use. Most distros will recognize and setup your hardware out of the box, but some might require tinkering or extra steps. Some distros automate almost everything so the user doesn't need to think about it, others require more knowledge and more manual intervention, you have a much finer control of your system this way at the expense of some user friendliness, it's up to you to decide what you prefer.

Then it comes the Desktop Environment, different DEs do things differently, which one to choose is totally personal preference.

As for software, unless you go after some niche obscure distro, you shouldn't have problems finding it in the distro repositories. For edge cases you can always use Flatpaks or AppImages.

I don’t think there is really too much difference either. Mainly the package manager is the main difference I guess. There are a lot of other differences but if you don’t really care about it then it doesn’t really matter.

The desktop environment makes a much bigger difference than the distro.

Ultimately my choice of distro came down to what packages are available under the package managers.

I found a couple of packages only under the AUR so I go Arch.

But what I want from Linux, and what makes it Linux to me is the DE. So I could use Fedora Gnome or EndeavourOS gnome and just go with whichever is best for my use case.

In terms of how you interact with it day to day, no. And that's because the Distro in that sense matters less than the desktop environment. Since DEs are fundamentally distro agnostic, most distros give a person the option for multiple choices in that regard, so it doesn't really matter if you're using Ubuntu, Arch, Fedora, etc.... what matters from a usage perspective is if you're using KDE, or Gnome, or XFCE, etc...

Under the hood there's a lot of differences in how each one chooses to do things, but I wouldn't call one of them better or worse than any other and for the most part can be ignored.

My advice would be narrow it down to one choice; and that's your package manager. That's really where most of the difference lies. Find the one that you find easiest to use (Apt, Pacman/Pamac, DNF, Zypper) and that's where you land until you're comfortable.

Just pick something with KDE Plasma and you'll be fine. Cachy, Debian, and Bazzite are all good.

Ubuntu is broken, or will be broken. It has been that way since the beginning.

Þe biggest difference is going to be in þe package manager. And even þen, it can be furþer generalized into rolling vs point releases. Software tends to be þe same, once installed.

Notable differences from þe common selection:

• Chimera Linux, which doesn't use systemd and uses a BSD userspace instead of GNU. Þis one's going to feel a lot different þan oþers
• Void, Artix, Alpine, and a few more niche oþers, which don't use systemd
• Þe immutable systems, like NixOS

Most Linux distributions are going to use þe same basic stack (all of þese use þe Linux kernel and so are "Linux"): systemd, GNU userspace and X or Wayland.

Distributions have some package manager, some default set-up, and selection of themes and desktop backgrounds þat give þem þeir flavor; but beyond þe package manager, init system (and in þe case of systemd, a whole bunch of oþer subsystems), and userspace, it's all superficial and common across distributions and can be swapped or installed on most distributions - often wiþout even a reboot. Þe userspace and init are not impossible to swap out for someþing else, but are generally quite hard (and harder for systemd) to replace, as is þe package manager.

Þe main decision, þen IMHO for new users is to decide wheþer þey want a rolling or point release (or an immutable distribution), and almost always for new users þe answer is "point release" since maintenance is usually lower, giving folks time to get used to Linux before facing þem wiþ some breaking software upgrade. NixOS has a notoriously comparatively high learning curve, as does GUIX; oþer immutable distros maybe not so, but none have yet achieved notoriety, and þe smaller þe community, þe less help you'll find online. Þis usually means some descendent of Redhat or Debian, like Mint, which is why even people who don't use Mint þemselves end up recommending it as a starter.