Replying to my comment above to update with what I guess is a solution for my issue:
I learned that Collector and Field Maps really don't like it when you create relationship classes based on user-maintained relationships, such as I had done with my coded domain join field. Documentation recommends creating relationship classes using GlobalIDs instead, so I re-architected my stack and re-published it to AGOL with the relationship classes now based on GlobalID/GUID.
The stack includes 3 items:
- Hosted Table of Apiary Owners (using GlobalID in the R.C.)
- Apiaries Point Feature Class (using ParentGuid field in the R.C.)
- Apiary Complaints Point Feature Class (using ParentGuid field in the R.C.)
The Apiary Complaints FC was empty, and the Apiaries FC had ~150 points in it, and the hosted table had ~50 entries. When I re-published to AGOL, I was still seeing the "No visible layers" error in Collector and Field Maps.
I tried re-uploading the stack, this time with completely empty point feature classes, and then appended my ~150 points into the Apiaries hosted feature layer after it was already published. This seems to have solved the problem - I am now able to successfully collect points in Field Maps/Collector.
I guess the take-away is that if you are going to be utilizing relationship classes in a Collector/Field maps configuration, make sure your feature classes are totally empty before publishing.