[gpapilion]

This is not true. Almost all firmware is signed by every vendor, and there are standards from Intel and amd on implementation of code signing.

Look up Intel pfr.

[buildbot]

Signed ≠ enforced.

At least for 4677 Intel stuff, gigabyte & HP and others let you modify the firmware and flash it.

[kj4ips]

HPE at least makes you flip a DIP switch, otherwise it complains loudly and halts.