Linux

I use Bluefin myself, and it’s honestly been game changing. Using an immutable distro has been the greatest quality of life upgrade in my 15 years of using Linux.

Also, if you use distrobox (automatically installed with Bluefin, Aurora, Bazzite, etc.) you can even setup an Arch container and continue to use the AUR. I use Steam installed from within an Arch container and it doesn’t feel any different from a natively installed app. It also means I don’t have to use the Steam flatpak which I had a couple issues with.

OP, another vote for this one.

It addresses your concerns in a wonderful way:

• Reliability; While it's far from unique in this regard, I'd argue that the uBlue distros are one of if not the most reliable desktop Linux experience that's currently out there. You know most of the drill already (read: built-in rollback functionality, clean base system). But, the uBlue project has some aces up on their sleeves that (to my knowledge) are pretty unique:
  • "Ninety (90) days of image archives allowing for flexible rollback options." The images are stored online, so they don't even take space on your device.
  • Shared community maintenance, i.e. even if upstream has a rare fuck-up, you can trust on uBlue's maintainers to deal with it without you even noticing. For a recent example of this, we got this.
• Access to the AUR; while Distrobox can be installed on any distro, uBlue projects come with perks that make the whole experience better than it's found elsewhere. From quadlets that have been properly setup from the get-go so that you don't have to (additionally) maintain those distrobox containers, to even minor things like including Boxbuddy OOTB to make the transition as easy as they come.
• Setup for Gaming; It goes without saying that Bazzite is excellent for gaming. It's gaming-ready OOTB and includes (almost^[1]^) all the performance tweaks you'd wish.
• Setup and forget; I (almost^[2]^) don't know any other distro that better embodies this than Bazzite (and its other uBlue-relatives).

All in all, I think Bazzite is definitely worth a look. Consider installing it and setup to your heart's content. If -at any time during or after that process- you come across an insurmountable^[3]^ issue caused by its atomic/cloud-native/'immutable' nature, then you can check it off your list and look elsewhere.

1. CachyOS is still superior in this regard by doing a better job at inching out (literally) every performance gain out there.
2. Perhaps Endless OS does an even better job at this, but that would be a bad recommendation for all the other reasons.
3. Before giving up, if you wouldn't have done it by then, at least consider contacting the community through their Discord server. They're very helpful. FWIW, Bazzite has pretty excellent documentation as well. (Even if it ain't as exhaustive as the even more impressive ArchWiki. Granted, it doesn't have to be as expansive.)

Literally said they don't want immutable.

It has been some time since I gave this a proper look. Do you use this yourself? If so, would you be so kind to share some of your experiences?

I never wanted a hobby, but rather an operating system.
That's exactly how I'm starting to feel. I was a "distro-hopper" when I was new to it, but now I just want shit to work. The only thing stopping me from pop is the state of their distro at current time. It feels like it's been abondened or something. I know they're busy with cosmic, but that's what it looks like. Also, I'm a kde plasma only person. I just can't use anything else.