>Perhaps secure boot by itself isn't enough, but I would imagine it would be a relatively large bump, when combined with a kernel-level anti-cheat

VALORANT also adds TPM to the mix alongside SB and a kernel AC and yet is still trivially easy to cheat in as long as you have a driver you can use. Granted, it needs to be signed (=financially unreachable by a big part of the community), but if stubborn enough...