We had originally planned to go all-in on passkeys for ONCE/Campfire, and we built the early authentication system entirely around that. It was not a simple setup! Handling passkeys properly is surprisingly complicated on the backend, but we got it done. Unfortunately, the user experience kinda sucked, so we ended up ripping it all out...
If you’re paranoid about this, go buy a yubikey and use that to secure your device/access to your passkeys. Being able to secure your own data instead of relying on the admin who may or may not know what they’re doing to secure the server is an advantage of passkeys.