RA is a shortcut companies are taking to market for privacy and security while not mentioning lock-in, network effects and DRM. When pressed, they will ultimately still say privacy and security aren't 100%.
That said, could a Linux distro come out with the same thing as these PATs using IMA/EVM/TPM/ME/PSP? Probably (Graphene has some support for RA, but I haven't looked in depth), and as long as Cloudflare had multi-platform support, and the implementation still allows letting me have control, I wouldn't see the problem. Bugs can be exploited by anyone with the know how, and I see no reason why I should give up control because companies want to take a shortcut instead of designing proper systems.
We see Epic has already said they won't support Linux because of anti-cheat, so that scapegoat exists, but there are other games that didn't go that route! Porting costs, and size of install base are real excuses among others, but anti-cheat is a BS excuse. No shortcuts by companies and no short cuts by platforms, but we know lock-in, network effects and DRM are too good to let go.