If you can 'see' the disc media and the external USB Apple superdrive
in Disk Utility, you could probably use that utility to eject the disc...
There is an eject icon or menu option in Disk Utility to eject stuff.
In the Disk Utility workspace you can usually see a list of items and
connected USB devices. If SuperDrive appears, click on its name or
use available means to specifically direct the Utility to show the Media.
You should be able to eject the Media, if you can see the SuperDrive
in Disk Utility.
And if you cannot see the Apple USB SuperDrive in Disk Utility or in
the system profiler (about this mac, more information, hardware) it
may be the SuperDrive has failed or somehow is not supported.
There is a repair guide at iFixit.com (mac devices) for replacement of
the optical drive, which is inside the Apple USB SuperDrive's case...
see the answers (as applicable) in the section beneath guide link:
To remove/replace the Optical Drive from Apple USB SuperDrive case:
• Optical Drive replacement - ifixit guide
Not sure what is going on there, either software or hardware.
Be sure the Apple USB superdrive is positioned correctly...
Good luck! 🙂