I have been using onlykey for past few years and just recently decided to try and use it as U2F.
I first tried it on proton mail, and it works fine. However, when I backed up the onlykey and restore it to my backup onlykey, the backup onlykey failed authenticating U2F. Does this backup not support backing up whats needed for U2F?
This is why I won’t use yubikey’s, because I can’t backup and I refuse to have to login to 50+ websites just to register a new key I bought.
You can backup and restore device and U2F should continue to work. Make sure to only use one or the other device though, don’t regularly use both backup and restore device with the same account. Make sure to connect OnlyKey to the OnlyKey app after doing a restore.