This isn't in defense of Nvidia (not by a goddamn long-shot: I haven't bought an Nvidia product in 20 fucking years), but everyone should assume everything new enough to contain an IME or AMD PSP is compromised.

Frankly, even if you stick with older hardware, the only way to be sure would be to build your own computer from scratch using discrete logic and then boostrapping your own custom C toolchain on it to cross-compile for your real computer in order to avoid the Ken Thompson hack.