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:
[Notice for Administrators] One of your themes or plugins needs to be updated to ensure compatibility with upcoming Discourse core changes. (id:discourse.hbr-topic-list-overrides) Identified plugin: โdiscourse-locationsโ
Maybe it still means the same or maybe other things turned up.