never heard of nitro key but i do use yubi key . Do you have any link for backing up these hw keys, my assumption is yubikey is backed up by yubi key only . When you scan the code to get 2FA enable , scan again with another yubi key to create a backup. This way if one fail then you have another. Dont know if another better way exist. nostr:npub1gxsss485j5yvwe7yffp48ddxr7qhshmzl9f8fvzrphltaj5zqaps8xkyrv or yes you can have any brand to backup