The Active Only checkbox and the progress bars are two different things. I was aware of two issues:
one with the Active Only checkbox not displaying a spinner - Bug #37133: /katello/sync_management tries to use /assets/spinner.gif but that's 404 - Katello - Foreman;
and one where the progress bars did not show progress - Bug #37442: Repository synchronization progress does not get updated in real time on Satellite Web UI's "Content ---> Sync Status" page - RHEL8 Satellite 6.16 - Katello - Foreman
However, I did not realize you were reporting that the Active Only checkbox does not work at all. It worked for me after the second fix, so perhaps it is resolved by that? If someone on nightly could test that would be great. In the meantime I have untriaged Bug #37442: Repository synchronization progress does not get updated in real time on Satellite Web UI's "Content ---> Sync Status" page - RHEL8 Satellite 6.16 - Katello - Foreman for possible backporting.