This works on Windows and Mac Firefox, you’ll get a prompt from the operating system to enter your credentials (e.g. PIN, biometrics) and it will save or retrieve the passkey.

The Apple implementation is poor and relies solely on having an iCloud account, which if it is disabled by enterprise policy means you needlessly cannot use the feature.

I had constant problems with duplicati and switched to kopia with backblaze and it has been problem free, so I would tread very carefully with it. The database would work for a while and then get into a state that required a reset and would not have permitted a successful backup to be restored.