Unless I missed something in the article this seems like a different issue. The article is specifically about the domain "immich.cloud". If you're using your own domain, I'd check to ensure it hasn't been actually compromised by a bonnet or similar in some way you haven't noticed.

It may well be a false positive of Google's heuristics but home server security can be challenging - I would look at ruling out the possibility of it being real first.

It certainly sounds like a separate root issue to this article, even if the end result looks the same.