I made games primarily for Windows which we also compiled for Linux. It is mostly input/output stuff, aka hardware issues. That is, audio issues, input issues, storage issues, dependency issues. Modern game engine mostly handle the rest. It wasn’t such a big deal to fix, but most gamedev lacked experience with Linux, and most projects are already over budget and late, so fixing Linux for an extra 2-5% of sales didn’t make much sense at small scale. Proton kind off fixed all of this tho.
You can live off minimum wage in Canada in some regions, if you’re children-free. It gets harder with kids, though the state will cover some of it of you’re low-income (Like a couple hundred per months, and virtually no income taxes).
Virtually no anticheat worked on Linux just a few years ago except maybe Valve and Blizzard in-house solutions. Games that are out and already committed to a specific anticheat can’t do much but to wait, so it is not really on them. Changing the anticheat solution mid-way on a released game would piss off so many people you can’t imagine. On a brand new game though, I would agree that this should be considered.