My specific concern is the "tied to a device". The only devices that seem to support the keys are proprietary devices, that only offer to backup the passkeys t

My specific concern is the "tied to a device". The only devices that seem to support the keys are proprietary devices, that only offer to backup the passkeys to their proprietary services. I can't see myself using this unless I can store the passkeys in my own keepassx (or similar) system, that I can manage 100% the backup, replication + storage of myself, without any assistance from a 3rd party.