Just an update.
Unlike others, I was able to get an external CD drive to boot on a very new Mac Mini. If Apple had disable that sort of thing, they undid that recently.
I have all my other external disks disconnected. The only disks are the SSD and the original 1TB HDD.
I’m wondering if it would be worth the trouble to try connecting a PC USB keyboard while booting up the CD. I could try that if I could find a neighbor with a spare one.
The USB ports in this machine are USB3. Could that have something to do with the problem? The external CD drive goes thru those ports, but that is at POST time. It’s possible that once Linux is running the default drivers can;t talk to a USB3 interface.
Thanks in advance for any help you can give…
