tl;dr if you boot Mastodon without LOCAL_DOMAIN once, you might be unable to fetch posts from some other instances. If searching for a post URL returns nothing, try running bin/rails r 'Account.representative.update!(username: ENV["LOCAL_DOMAIN"])'. That fixed things for me. So. Four hours of debugging missing posts later, here we are. The symptoms I noticed were: some posts were mysteriously missing on my server, even though they clearly existed on other servers posts that did appear were so...
