I’ve just tested your sg module suggestion and it shows that:
Removing the module (sudo rmmod sg) then running MakeMKV results in the “can’t find any usable optical drives” message.
Re-adding the module (sudo modprobe sg) then re-starting MakeMKV results in the drive being found.
So clearly this module is the important one. Though a reboot isn’t necessary. I don’t have anything in /etc/modules-load.d telling it to load; there’s a file /usr/lib/modules-load.d/cdrecord.conf containing sg, installed as part of cdrtools.