But isn't all client-side anti-cheat bypassable by doing image recognition on the rendered image? (either remote desktop or a hardware-based display cable proxy)
FaceIT essentially has countered most modern cheats including those using DMA. https://www.faceit.com/en/news/faceit-rollout-of-tpm-secure-...
Nowadays if memory access is needed, you are looking at having to find a way to load a custom BIOS or UEFI module in a way that doesn't mess with secure boot. Even then, certain anti-cheats use frequently firing interrupts to find any unknown code executing on any system threads.
At that point you have to look at heuristics (assuming the input device is not trivially detectable vs a legit one).
However, that can obviously only be used for certain types of cheating (e.g. aimbot, trigger bot (shoot when crosshair is on person)).