I've dabbled with Linux over the years, first with Ubuntu in the early 2010s, then Elementary OS when that dropped, and a few years ago I really enjoyed how customizable the gui was with Xubuntu. I was able to make it look just like WIndows 2000 which was really cool.
Which current distro has the best GUI, in your opinion? I find modern Ubuntu to feel a little basic and cheap. I guess I don't really like modern Gnome. I'm currently using Windows 10 LTSC which is probably the best possible version of Windows, but I'd jump to linux if I could find a distro with a gui that feels at least as polished and feature rich as Windows 10 LTSC.
You can use most desktop environments on most distros.
If a distro has its own GUI and it doesn't exist on other distros, usually that means either it isn't free software or it's not good enough that anyone has bothered to package it for other distros.