How about this:
- Add ability to make custom "servers" (which can be just rooms on your proprietary server) with no anti-cheat at all, just fool around with your friends and do whatever you want, mods/hacks/cheats/etc.
- At least for casual play modes, make protocols that are less reliant on clients to do the right thing and instead only tell the clients more or less what the player should know already. This might leave some room for sweaty tryhard cheaters to consistently beat other people, but in a casual game which is mostly just for fun this doesn't really matter.
There may be some places where a protocol-level solution is not feasible. In that case yeah, require your anti-cheat, but only for competitive game modes. I wouldn't even be pissed if they didn't allow it to run on Linux, Linux makes it easy to do whatever the fuck you want with your computer and so a determined cheater will find a way to cheat. It sucks, but I feel like a lot of people don't really care that much about sweaty competitive game modes anyway. Just give me a way to fool around with friends, it's not that serious FFS.