Unable to install firmware update?

Yes.

Not exactly. This is a Ryzen PRO, so it’s AMD and not Intel.

Curious. Those are the only things about my system that I would think to be “non-standard”, and I have vPro features disabled.

I have two generations of ThinkDock I use with it and fwupdmgr has been able to update both of those, too.

This is a guess, but I think there might be some specific firmwares that can’t be updated with Secure Boot enabled.