KeePassXC "supports passkeys" but the website/app that offers the passkey needs to offer it in the correct way for KeePassXC to ingest it. I've found a fair amount of scenarios where they don't correctly let you drop it into them.
Until I can have all my keys as cleartext in a text file, I won't use passkeys.
Until I can have all my keys as cleartext in a text file, I won't use passkeys.