Email received. Thanks much, agent_kith!
Got the new kernel uploaded with no incident, but cannot get it to stay as the boot kernel for my system. I know, I know: why on earth does this guy have so much trouble...
The Boot Kernel section does show two items in the dropdown: 5.4.0-89-generic or 4.4.9-rt17-amd64-ng-mytek. I select mytek, of course, click Save and reboot but the 5.4.0-89-generic just keeps coming back. I saw a segmentation fault after one reboot, but just once and have not had it again.
I did notice that when I change the Boot Kernel and click save, the boot kernel changes back immediately before I can even reboot the OS. Might be related.
I am using version 1.2.0. I suppose I could update to 1.2.1 but was just trying to keep my problems isolated before upgrading.
As always, I'll keep chipping away at it.