Mint was my first thought as well. Haven’t used it myself but in the past I’ve heard that it’s supposed to be very user friendly and stable, though I’m not really up to date on Linux distros so I wanted to check if this was still was true (which is seems to be) and if there were any new options.
I’m using Fedora KDE on my own PC, and it has been soft-bricked by updates multiple times, or by doing seemingly trivial things like choosing a theme from the built-in store. Seems quite unstable to me so it’s not something I would recommend to someone without the ability to repair their OS from a terminal.