I use FBReader everyday. When you say that it’s netblocked, what do you mean? I’ve been able to use it in airplane mode with no issues. I’m using v3.7.6.

I’ve had this issue before. My limited understanding is that your home server fetches copies of communities somebody on your server is subbed to. But if you’re the first person, it can take it a few hours to federate (took mine a day.)