There's also plenty of folks combining this with TPM and boot measurements.
The ugly part of SecureBoot is that all hardware comes with MS's keys, and lots of software assume that you'll want MS in charge of your hardware security, but SecureBoot _can_ be used to serve the user.
Obviously there's hardware that's the exception to this, and I totally share your dislike of it.
Right, but as engineers, we should resist the temptation to equate _possible_ with _practical_.
The mere fact that even the most business oriented Linux distributions have issues playing along SecureBoot is worrying. Essentially, SB has become a Windows only technology.
The promise of what SB could be useful for is even muddier. I would argue that the chances of being victim of firmware tampering are pretty thin compared to other attack vectors, yet somehow we end up all having SB and its most significant achievement is training people that disabling it is totally fine.
An unsigned hash is plenty guard to against tampering. The supply chain and any secret sauce that went into that firmware is just trust. Trust that the blob is well intentioned, trust that you downloaded from the right URL, checked the right SHA, trust that the organization running the URL is sanctioned to do so by Microsoft...
Once all of that trust for every piece of software is concentrated in one organization, Microsoft, Apple or Google, is has become totally meaningless.