I for the life of me couldn't get synapse's (matrix's) federation to work. It said that the encryption couldn't be trusted, i could join public rooms but i couldn't start any chats, i couldn't invite people to my rooms, i couldn't get invited to rooms.
and go all the way to the bottom or search for `trusted_key_servers`. it's probably going to be `matrix.org`. You should change it to the following by removing `matrix.org` and leave blank square brackets: