Diablo and Diablo 2 (not Resurrected)
I think Diablo 2 even came with an extra disc specifically so you could give it to your friend to play via LAN. Then these fuckers removed the option in Resurrected even though they promised they wouldn’t.
StarCraft and the old Warcraft games work via LAN as well.
Quake, Doom, Unreal (Tournament), Half Life
KDE Plasma has been getting so much more efficient with every release that you can almost recommend it for low-end systems.