Hi,
I upgraded my laptop to macOS 15.3.1 today (from 14.x) an noticed that I can no longer use WebAuthn with a Yubikey as a second factor when trying to log into the Proxmox UI.
After deleting the YubiKey as a second factor, I can also no longer re-register it when using Safari. Chrome works fine. Please see the attached screenshot of the error message:

I guess there are some new restrictions in the new Safari version.
I upgraded my laptop to macOS 15.3.1 today (from 14.x) an noticed that I can no longer use WebAuthn with a Yubikey as a second factor when trying to log into the Proxmox UI.
After deleting the YubiKey as a second factor, I can also no longer re-register it when using Safari. Chrome works fine. Please see the attached screenshot of the error message:

I guess there are some new restrictions in the new Safari version.