I had to enable “USB hard drives” in the regular bios setup to get access to them in the F12 menu (Thinkpad L480). Not in front of me at the moment but on the “boot” or startup page there was a sort of unintuitive to find “boot” menu that looked like a page header that lets you enable or disable boot devices. USB was disabled by default.
I’ll second Mint, though I haven’t done much gaming on it. Before switching all my stuff over to Mint, I did have xubuntu/steam running pretty well for most games I tried up through Doom 2016 (can’t remember if I tried eternal) so I can’t imagine mint being much worse. As far as gaming specific stuff goes it’s got a pretty decent driver manager and time shift preinstalled for when said driver manager breaks things.