Edit: And in the end, it's back to good old Fedora with Xfce. I guess I'm an old man, fixed in my ways. Haiku was interesting, but not nearly as stable as needed. OpenSuSE with Xfce was rough, it requires more polish.
I've been a Fedora Linux user for a million years by now, and I haven't touched any other OS (outside of Windows 10 and 11 at work).
Lately I got a refurbished ThinkCentre from ca 2018 (7th generation Intel i5, 16GB RAM, Intel HD 630). The initial idea was to use it as a media PC but the small form factor ended up not being small enough for my living room.
Now I'm thinking of using it as a desktop PC for a while, to see if it can make my laptop be a portable machine again instead of always plugged, always on. If it doesn't work out, I'll use it as a home server.
Since this is all an experiment, I want to give a new OS a shot before I settle for the familiar Fedora.
OpenSuSE is the first on my list, but even from the LiveUSB I noticed that the software selection is more limited than I'm used to.
I'm thinking of giving HaikuOS a shot as well.
What else has been going on in the world of free OSes since 2007? What's one that you are excited about?
If you're looking for something to keep it as libre as possible, then Debian is a great choice. I know Fedora by default keeps it that way, though you can install non-free software/codecs/etc if you want. Debian is the same way. And since Debian is the foundation of some of the biggest distros out there, you're pretty much always going to find packages for what you need. And if you go with Debian Testing or Unstable, you can get a bit more recent packages, and I've never found them to be really "unstable." Wouldn't run them on a server, but a desktop is totally fine.
I do like some of the suggestions here for FreeBSD or OpenBSD. If you were to go that route, I'd go with FreeBSD. Their documentation is stellar (though OpenBSD's is as well), the man pages are fantastic and actually helpful, and between the ports and packages repos, you'll generally find what you need. Plus things like ZFS, jails, etc. are great.