Which makes yubikey impossible to use with geographically distributed backups. You need the backup available at all times for when you want to register with any new service.

This is why you should use a device which allows exporting the seed, like e.g. multi purpose hardware crypto wallets.

Are you talking about SSH or a different setting?

With SSH, you can always share the primary and backup pub keys, even if you don't have the backup key handy.