> ...but many have weird bugs like crashing when you Alt-Tab out.

Would it be easy for you to compile a list of like five or ten games that do this? I'm curious to see if I can reproduce this on my Steam-on-xorg-on-Gentoo-Linux machine with an AMD graphics card.

I don't doubt your report, not even a little bit, but -personally- I've found window management on Linux to be light-years better than on Windows. I can put nearly every game I've tried in my huge-ass Steam library on fullscreen on another virtual desktop, flip over to some other desktop (or window) to check something, and flip right back to find the video game still fullscreen and still running happy as a clam. [0] (To say nothing of the total lack of Windows-typical jankiness when changing the screen resolution on an "Exclusive Fullscreen" game.)

Whereas on Windows, it's kinda a crapshoot regarding both what state your desktop will be in when you Alt+Tab out of a fullscreen game and what state that game will be in when you Alt+Tab back. And if that game is "Exclusive Fullscreen" and is not running at your desktop's resolution, all the windows on your secondary monitor are probably going to be rearranged when the game starts, and will definitely be rearranged when you Alt+Tab out and maybe then again when you Alt+Tab back in.

[0] Two very notable exceptions to this are Red Dead Redemption 2 (it notices that its no longer the foreground window and "helpfully" makes itself windowed) and the Linux version of Dead Cells (it "helpfully" minimizes itself when it's no longer the foreground window.).