No, we are not talking about the same thing. I see now, you're saying you got an external drive for the purpose of creating a backup, but StartOS can't see it. Almost certainly a formatting issue. You could probably format it ext4 and that would help. Also possible StartOS v0.3.6 (currently in testing) will recognize it because it as-is is based on a newer Linux kernel.
Are we talking about the same thing? I’m talking about the backup to physical drive feature.
https://docs.start9.com/0.3.5.x/user-manual/backups/backup-create#physical-drive
Discussion
Hmm, it is formatted to EXT4. Maybe it’s formatted incorrectly somehow. I’ll try again tomorrow.
Fixed it. I accidentally formatted the wrong partition. Followed this video: