Congrats!
How do the hunts compare to other games in the series? I haven’t played a lot of XIII, but I really enjoyed getting 100% hunts in XV and XVI, and I’m on the big XIV hunt achievement grind now. I’m sure I’ll want to 100% the hunts in XII whenever I get around to finishing it, too.
I’d recommend Bazzite. It’s a gaming-focused immutable distro. The base system is an image and updates are automatic; a 13-year old might already be familiar with this kind of system because it’s similar to how Chromebooks work. It comes with Steam and Lutris preinstalled. You can install additional software via flatpak.