Hello 
I am not sure and maybe I am wrong (I didn’t try it yet) but this is now a core thing? There is a new template a few month in discourse/templates called offline-page.template.yml and inside it it trigger the GitHub - discourse/discourse-offline-page: offline page for discourse · GitHub. Which is the static html site during Discourse loading. There is also a PR about it in discourse_docker FEATURE: add offline page template by featheredtoast · Pull Request #752 · discourse/discourse_docker · GitHub