It's unconscionable to tell users this is here to keep you safe, but that you have no control over it & if something goes wrong well then too bad, at best we might provide an update.
(Also that governments can probably force these root-of-trust companies to sign payloads to circumvent security is also pretty icky to me.)
Of course, if the key used to sign the firmware is compromised, the root of trust is still technically what it is supposed to do - verifying signatures, it's just that that it becomes irrelevant in terms of security / integrity.
The OP states that the vendors could have revoked the compromised platform key with a firmware update. They just didn't bother.
That does make it quite difficult to pull off any kind of key rotation. I'm not sure, but I think (well known Secure Boot tool) sbctl is saying that you can sign a bootloader with multiple keys, which would permit creating a bootloader that would work with the compromised & the new root-of-trust, which at least opens some window of possibility. https://github.com/Foxboron/sbctl/blob/master/docs/sbctl.8.t...