I just installed Wiki.js with Docker-Compose, following the official documentation. When I enter the address of my wiki, I get a very minimalistic html page, where something is clearly not loading:

It should display properly I guess?
I followed this tutorial.
The only specificity is that it lives behind a reverse proxy (a nginx container).
I literally have no idea where to start investigating: there are no error messages for the Mongo container nor the Wiki.js container. So, is it a known beginners issue? Have I missed that simple a crucial step?
https://docs.requarks.io/wiki/install/troubleshooting#weird-display-no-styling-missing-css
That's it! Thanks a lot :)