Ubuntu was a fantastic distribution to start early on. Especially in the pre-10.x days there weren't many beginner friendly ones. Your alternatives were Debian with very outdated software, SuSE which was kind of OK, Fedora which was also quite unstable and lacking packages (remember hunting RPMs on the old RPMfusion?) or Ubuntu. At some point I'd outgrown Ubuntu and moved on to greener pastures. Nowadays I'm not sure I'd be recommending Ubuntu to new users, Fedora is quite good and without all the snap store shenanigans. Even Debian installation experience is not too bad and it's not lacking too much in software.
I think PopOS is the new beginner friendly, just works, distribution. It's what Ubuntu should have been.
I also feel less worry about System76 trying to capture market share and then do a heel turn to monetize on that market share. We all know exactly where the money comes from for System76, and it's not selling support contracts
The other distro I tried out was openSuSE, but idk which version. It was shipped with KDE3 or 3.5, and man, I loved it. RPMs and YaST was something to get used to, especially after Ubuntu and I was like... 15-16 yeara old, barely just into Linux land so broke the shit out of them pretty regularly. But I learned a lot.
Then KDE4 and Plasma came out and I hated every pixel of it.
