How to fix "Could not connect to the database server" in myBB in Docker Compose

I seriously don't know why these projects don't have any useful documentation

I was trying to install myBB through Docker Compose. Because this is a true old school open source project, the usability sucks, the documentation is even worse and the community as unhelpful as you can be.

The Solution

If you’re using the default Compose file from here, the database address is postgresql. Not localhost, or the IP of the machine, or whatever crap the community wants you to believe. It’s postgresql.

Closing Words

Will I be using myBB? No. I was thinking of trying it out as a replacement for Flarum. But it doesn’t work out of the box with reverse proxies, you have to set the configuration of the built-in NGINX server manualy (??? what year are we living in again?), the community is filled with your typical Linux elitists, and after restarting the stack, it doesn’t even load anymore. So I’ll stick to Flarum.