Do we know if this is also the case for other systems that use Aspeed/ami BMCs, or if the key pair in question is exclusive to SM?
Supermicro is one of the only vendors that tries to prevent this attack at all through RoT.
Other vendors you can flash whatever unsigned firmware you want. It’s very useful for adding in microcode for intel engineering samples, or malware…
Look up Intel pfr.
At least for 4677 Intel stuff, gigabyte & HP and others let you modify the firmware and flash it.