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 using Android it’s more than likely just an OS issue. I have had a lot of issues on my phone trying to use passkeys let alone just the password manager.