I have a Mac and a user account with admin privileges. Someone else created another apfs volume (not startup drive) encrypted with FileVault. I do not know the recovery key. As an admin, how can I obtain this key?
For non-startup drives, the disk is encrypted with a single password and is not linked to a user account or iCloud, nor does it generate a backup key. Admin users are required to enter the same encryption password as any other user.
The best suggestion would be to ask the other person to unlock the drive or give you the drive password, which they may or may not be inclined to do.