Is it possible to have kernel-level anti-cheat in Linux?
Yes, Absolutely. But, people would throw a fit. There is probably no way to opensource it without also making it easier to bypass. There would be a concerted effort to reverse engineer it and remove it from the system while maintaining functionality
Maintainers of anti-cheat software are not volunteers. If there was an order from management to port the system to Linux, it would happen. It's just that with the Linux userbase as small as it is, it's simply not profitable to cater to them.
I think that if it ever happens, there will be a influx of people moving to linux, or abandoning their duelboots
I fully disagree. The thing keeping regular people away from Linux as an OS is not that they can't play some online game with Anti-cheat.
Linux is in a weird place right now. It's actually a perfect fit for non-technical users that use their computers for email, web browsing, and Netflix, but those users don't know what an operating system is, let alone that there are options. More technical users tend to require more specialized applications, and if there isn't a native linux port available, you have to do some research for alternatives, or to find a way to run it in wine.
Windows is shitty, but it's comfortable. And I know that it will run any software I throw at it with basically no research or troubleshooting.