I have been working for the last week on how to upgrade a large service with relationship tables to pop-ups of internal links.
Its an old service that has been stable with pop-ups to related tables with hyperlinks to drawings and as builts.
Pop-ups failed on a certain layer with the move to Experience builder and the Map Viewer (non- classic) I have narrowed down the feature layer pop-ups to failing due to grouped symbologies on domains that have changed.
I was working on configuring pop-ups for related tables. They did not work and had blank related table pop-ups when linked. If I deleted all the tables from the initial service and added them back one by one, they were configurable.
I was in the process of doing that when this morning's decommission of Classic removed all options to relate feature layers to tables. I swear the option to relate tables to feature layers was an option to configure yesterday at 4:00 EST, and the option does not exist on any of those layers today.