DD now has published a bugfix update for the DD Chicago landmarks scenery so this bug is solved now.
The conent manager not loading (if too much addins are installed in the community folder) is apparently a separate bug that is discussed here:
https://forums.flightsimulator.com/t/content-manager-wont-load-if-there-are-more-than-1028-add-ons-in-community-folder/502298/1