Pathfinder's compatibility is based on 3.5e, so DnD 3.5e homebrew stuff is likely to work with Pathfinder. 5e stuff probably will not.
Old Windows games are more likely to run successfully on Linux than Windows.
New Windows games supposedly run faster in modern Linux than modern Windows. I can't verify it, lacking a modern Windows installation, but tomshardware.com said it was true.
Most things in Pathfinder are more intuitive though, so it could be easier for them. D&D5e is full of contradictions and stipulations that you are forced to remember. P2e is, in comparison, fairly easy to remember how everything works. There may be more things to remember, but those things are simpler so it could end up being less in total.
Yeah fair there's loads of third party content for DnD. There is also for Pathfinder but not quite as much.
That being said, I've found the core system gives you more customization so there is not a constant need for outside content to keep the system interesting.
Yeah, you can make anything from classic knights, to mystery cultists, to fucking magical girls natively in 1e. You don't need a billion dollars of 3rd party supplements to make whatever you want, it's just there in Pathfinder.
Hilariously, getting better for both of them. Pathfinder has a lot of third party developers already, and gained some after the big D&D debacle when Wizards tried to update the OGL and kill third-party. Linux is still slow going, especially on the gaming side, but a number of FOSS companies and Valve have done a lot of work to legitimize Linux as a personal computing platform.