EndeavourOS meets all of those criteria except for the GUI package management which, admittedly, is unnatural to the Windows convert. However conquering that small, surmountable hump will unlock the AUR which imo is the real value add. There are many packages that are not included in standard repos that are included in the AUR. Regardless users can choose whatever they want. EndeavourOS is a great distro that is not complicated. It uses the calamares installer and ships with KDE. An afternoon of reading about how pacman works and installing yay/paru provides a great user experience and they will never have to do a system upgrade.

I recommend EndeavourOS to newbies because I’m biased towards Arch. I think it’s a relatively low BS distro that gets you up and running. You also have access to the AUR which is awesome.

If that seems like too much I’ve heard Linux Mint is dead simple and stable.