Ubuntu LTS. I chose it because it mostly just works and there's plenty of documentation and q&a online (StackOverflow)

As for the problems, on the desktop side I wish it was more polished. For some reason every time there's a wireless printer in the network it tries to reinstall it (fix: sudo systemctl disable cups-browsed), error reporting is annoying (fix: sudo systemctl disable apport), can't easily set full RGB out on HDMI (fix: xrandr --output HDMI-1 --set "Broadcast RGB" "Full"), volume change is laggy on some soundcards (fix: enable-deferred-volume = no) and small quirks like this.