Thank you! I am a bit out of business when it comes to programming. 
With a newer version of Discourse I installed/updated yesterday, the message changed:
[Hinweis fĂŒr Administratoren] Eines deiner Themes oder Plug-ins muss aktualisiert werden, um die KompatibilitĂ€t mit den bevorstehenden Discourse-KernĂ€nderungen zu gewĂ€hrleisten. (id:discourse.hbr-topic-list-overrides) Identifiziertes Plug-in: âdiscourse-locationsâ
Maybe it still means the same or maybe other things turned up.