I think this is the normal instance behavior of Lemmy instances. It would be too much load for small instances to sync everything in the fediverse. Instead a member of your instance needs to first manually find a community before it starts tracking and makes it automatically available to the other instance members from there on.

Few weeks ago I saw a really cool presentation about the history and current state of Linux phone. It is unfortunately in German, slides in English though: https://youtu.be/JeFoRE72Gu0