frollogaston parent
This attestation does require obfuscation (often via hardware), otherwise there's always a way for someone to force a positive attestation. Like run a modified kernel that tells the game it's unmodified.
Requiring a key to be practically impossible to extract from hardware doesn't require obfuscation to be effective.
The hardware itself is obfuscation.
What you're asking for does exist though, in the form of Android devices and game consoles. Was curious about Steam Deck and... turns out it doesn't have secure boot. Someone could build a desktop OS on top of an anticheat-friendly kernel, but it'd probably not be big enough for gamemakers to care, and Linux desktop people would be uninterested in it to say the least. (I'm on a Mac btw, I have no horse in this race, just understand people who do)