@gvde glad the applicability is working again.
For @Laszlo (or anyone else following along), after applying the Pulp PR I mentioned above and restarting all of your Pulp services, you can do the following to regenerate applicability for all hosts:
First: foreman-rake console
Then:
ForemanTasks.sync_task(::Actions::Katello::Host::GenerateApplicability, Host.all)