There’s no way to meet anticheat standards on Linux. It’s inherently a less secure platform for all the reasons you love. That’s not a dig against the OS, it’s a fact that enabling Linux in anticheats makes it less secure on all platforms due to the level of open customization Linux gives. That’s great for the user, but a pretty much unsolvable problem from game companies.
I don’t use FOSS most of the time because it doesn’t meet my needs. My standards are too high for Linux by your logic then.