Agree completely with your concerns with regards to lost/stolen keys. Most of the places where I've been able to use my Yubikeys (FIDO2) also offer a very clea

Agree completely with your concerns with regards to lost/stolen keys. Most of the places where I've been able to use my Yubikeys (FIDO2) also offer a very clear list of enrolled/registered keys, along with either a hash or serial number of the key. It makes revoking a key pretty easy in my experience. I'm less keen on the idea of centralized repo for dead keys - each key is unique to the site in question, so there will be no need to share the existence of that revoked key's identifer with other providers - the data is meaningless to anyone else.