For anyone who might care, two things solved this problem for me and allowed me to print on discs.
First, a shout-out to the Canon Tech Support phone guy (maybe Bill was his name?) who was super-conscientious and helpful and kept at it until we successfully printed a disc. These days there are lots of frustrating experiences with tech support so it's great to have a really satisfying experience. Canon: Give that man a raise!
Anyways, the first thing I needed to do was to go into my Apple System Settings and click on "Printers & Scanners." It was showing two listings for "Canon iP8700 series." One of them had an Apple driver. I had to delete that one and keep the one that was showing "Driver version 16.80.0.0" (or whatever is the most recent driver version downloadable from the Canon site).
The other change was in My Image Garden. Under "Settings" (what Apple is calling Preferences now), it showed that the "Print/scan using AirPrint" box was checked (or active). According to Bill (?), the default was supposed to be unchecked or inactive but that might have changed with a recent update. Anyway, I unchecked the box, clicked print and was good to go.
Again, much thanks for a satisfying tech support experience in 2024, Canon!
