My late-2010s home laptop runs Debian 11, because strangely nothing else will boot anymore.
My late-2000s ThinkPad runs Arch, because I like pacman and a ThinkPad like that needs a hackery OS. BSD, Slackware, Void and Gentoo would also fit, but I prefer Arch.
My mid-2000s MacBook runs GNU Guix. Not really sure why I picked it, but it's a working system on fussy hardware, so I'm happy. However, being a Mac, this doesn't really count as a PC.
I used to be able to run everything from Trisquel to MS-DOS; but it's gone a bit funny recently. Debian and its derivatives are the only thing that works now. Funnily enough, Win$hit doesn't boot anymore either!