just reproduced this today with an USB key with a vfat partition as the target device (instead of a SATA disk)
ubuntu@ubuntu:~$ sudo os-prober ubuntu@ubuntu:~$ (no output)
If I select another choice then Erase and use entire disk again, the warning disappears
just reproduced this today with an USB key with a vfat partition as the target device (instead of a SATA disk)
ubuntu@ubuntu:~$ sudo os-prober
ubuntu@ubuntu:~$
(no output)
If I select another choice then Erase and use entire disk again, the warning disappears