I do not know coding and dev-world at all more than I did one hello world thing with Visual Basic long long time ago. But I can do some things, because I know better how to admin my WordPress and Mastodon/Pixelfed servers, and somehow my Discourse. Plus out there is thingy named AI (that isn’t such easy for a novice than is advertized).
I don’t know if this is even remotely possible with Discourse because of Docker, but in ordinary Nginx-Varnish-WordPress world I build a system where a plesk server gets information of 50x error and shows an error page. Actually I have three setups, where frontend nginx shows generated snapshot content if Varnish is down, Varnish starts use snapshot for uncached content when WordPress-related backend is down and third one is error page if frontend nginx doesn’t answer.
Varnish things aren’t possible for Discourse, but I can’t see any reasons why one couldn’t build such spiderweb into Docker-world too where any 50x error would show an errorpage.
That could be very error prone system though. And I have no idea what so ever what would happend if there is more than handful users.
There is the most obvious answer too, of course: has i.e. Nginx before Discourse. I used that before I moved on to 2-container.