Not every Yubikey supports the resident keys. All my Yubikey 5 keys have too old firmware, which AFAIK cannot be updated, so this is not a viable solution for lots of people even if they own the hardware. GPG just works, and can be used for many other things while one's at it already.
Absolutely. We're trialling this for our SSH bastion server. The security keys don't need any setup at all, which makes it much easier to handle backups and replacements.
Let me rephrase: GPG is possible to get working, the resident keys are not, regardless of the amount of setup. Though the other comment seems to suggest it might not be the case, so maybe there is hope.
You should be able to just use a website that uses resident keys (such as Microsoft Passwordless login). I don't think the UI is any different, it's just that the key will actually get stored on the device.
Because the first firmware revision lacks the credential management API, there's no way to list the resident keys on the device or to delete individual keys. The only way to delete resident keys AFAIK is to reset the FIDO2 application on the key.
