The equivalent for AMD CPUs is called the Platform Security Processor (PSP). I am not aware of a way to disable it.

I don't know about Apple CPUs but they definitely have co-processors running besides the main CPU.

In fact, many people talk about the IME but the practice of having proprietary systems with their own privileged hardware is the norm nowadays. Another example is the "baseband" processor in phones, it is a complete proprietary system with its own processor, OS, etc... and it controls the modem, among other things.

I’d like to know more about AMD specifically too. I’m well aware that PSP is their equivalent but there seems to be so little information out there about it. Is it really an equivalent? Is it as bad as ME? Can it be disabled? Does it have the same level of access as ME? Have their been any exploits of it yet?

The wikipedia page is rather bare. There’s a couple of papers linked to but frankly they go over my head. Is there any respectable analysis out there?

AMD relies on ARM's Trustzone to do this.

"The PSP itself represents an ARM core with the TrustZone extension which is inserted into the main CPU die as a coprocessor."

https://en.wikipedia.org/wiki/AMD_Platform_Security_Processo...

Apple has Secure Enclave. Who knows what that's doing.