Web Developer
The version of docker-compose.yml in the self-hosted instructions uses the image appwrite/console:6.0.13 for the appwrite-console container. This version of the console has a bug which means relationships cannot be established between collections in Databases via the UI (the collection drop-down always shows no collections available for selection).
Updating the image to version 6.1.2 seems to have fixed it for me, although it occurs to me that I'm not sure how to know whether or not I have the right version, as that number seems arbitrarily different to most of the other appwrite/* containers in the same setup. I also would prefer to not have to deviate from the officially-supported file if I can help it.