edit: Fedora it is then!
He will be running the AMD 9800 X3D w/ RX 9070 XT, B850 motherboard.
I am deciding between either Fedora (probably KDE) and Bazzite (also KDE), but I’m not sure whether an atomic distro would be better/worse for a newbie.
As far as I understand, atomic distros can be easily rolled back after an update, but you are unable to use apt/dnf/etx, you need to use Flatpak, I think. Would that be limiting for the average user? Also, does Bazzite have better driver support for newer AMD hardware compared to Fedora?
It has to do with LTS kernel (iirc) making it incompatible with certain new(er) hardware. I recommend Fedora KDE.
Mint is based on Ubuntu, which has a Hardware Enablement Stack offering newer kernels. I would expect that (or maybe something Mint-specific) to take care of it.
I still would never recommend a “stable release” or LTS distro because the vast majority of security vulnerabilities never receive a CVE, and as a result the a large amount of vulnerabilities go unpatched for months. Also I like distros that take security seriously (Fedora and openSUSE).
Usually they backport security fixes to the stable version.
As I mentioned, most security vulnerabilities are not reported because it may not seem security related. The distro maintainers can’t keep up with every package and read all the commits, so as a result security fixes often go unfocused. It is a real big problem that many security researchers acknowledged.