So, here I am: tail between my legs, with the apparent knowledge that some months ago, I must have changed a setting that's now preventing me from doing something that should be easy...
I've read the instructions / watched the videos on how to make a course available to users who are not logged in. Triple checked everything, and it just doesn't work. The only thing I can imagine is that in a sudden fit of security consciousness, I disabled something that's now killing me.
Specifically, when I turn on Guest Access for a course, then enter the URL for that course, I get "This course is not available to students". It's not hidden, and the availability dates are not enabled - I have no ideas.