Your account lives on the server you registered in. You can’t use it to log into other servers but you can interact with communities and posts in other servers (I’m from sh.itjust.works posting on sopuli.xyz). That’s my understanding anyways. I think the spinning button is a bug, I ran into it as well when registering an account

Arch Linux. It’s too convenient. The AUR hosts a massive amount of packages, wiki is super detailed and covers solutions for all sorts of edge cases. Needs a bit of tinkering to get started but once things are set up it’s very stable, and still gives you a lot of freedom to tinker with your system however you want. The only other option I’ve considered is NixOS which has some pretty interesting features