The games run in all ubuntu or is some especific?

Welcome to the general discussion! Which game are you talking about? There are subforums for the games too but some topics better posted here.

I think GOG stopped actively supporting Linux several years ago which why most games state you need an outdated version of Ubuntu.

some games run in ubuntu with minor adjustments but any linux system is a mess mash of options and nothing is certain

in general however Ubuntu is a Windows look alike for basic computer users so its well supported and if you just want a linux system to play games on thats the one i would go with

AFAIK the linux installers work in most major distributions of Linux. There may be a few libraries that you also need to install depending on the game and your distribution. If you run the installer and game from the terminal you can see any error messages and work out which libraries are missing, if any.

I sometimes have better luck running the Windows version through WINE than using the "native" version.

WINE is really good these days, btw. Valve's work on Proton has mostly been upstreamed into WINE itself, and when combined with stuff like DXVK and VKD3D playing Windows games on Linux is almost perfect, as long as you stay away from the big multiplayer games.

Most of the games are still working. Some of them have fallen apart due to outdated libraries, but even those can be solved by pruning an errant file or two.

It'd have been nice had Fedora backed a winner like Arch, OpenSuse, or hell even the boring as it gets Fedora.

You can stick a fork in that ancient version of Ubuntu that GOG are so attracted to. Fedora have most certainly backed Fedora.

gog didn't stop supporting linux.

I can't think of a single game on GOG that can not be run on Linux. But I would prefer the Windows version run thru WINE or Proton over the Linux version of most games.

Its more future proof and has more features that way.

With enough tinkering, you can run pretty much any games from GOG on any modern Linux systems, if that's your question.
But yes, Ubuntu and its direct forks, such as Mint, still tend to be more straight forward for setting up than "distant cousins".
But worth noting making methods for making games work are not always obvious, some times even requiring emulators, virtual machines or source ports.

I have had really good results using bottles (a fancy front-end for WINE and Proton). My experience has been that native Unix ports of most games tend to get the short end of the stick, so to speak. While the Windows versions are updated, oftentimes the Unix port is not. All of my GoG games are Windows versions, which I run via bottles (by box is Ubuntu) pretty much flawlessly. In the interest of full disclosure, my box is not anywhere near top-o-the-line (anymore, anyway): Intel i5 using a NVidia GTX 1050ti... As always, YMMV.

Mongo