Debian with KDE, Elementary, or PopOS.

These are very beginner friendly setups, I'd pick Debian for long term stability where you don't have to update much. I'd also recommend KDE/Plasma due to familarity with Windows UI, as it's much easier getting used to than GNOME.

Elementary has a MacOS look and feel, with nicely integrated default apps (in terms of UI design) so depending on taste I'd pick that. PopOS has a fairly nice integrated UI, too.