It's important to raise up alternative media, as others are saying in this thread, but frankly I don't think that's enough, I think we need to attack and discredit existing media, until the general public distrusts them as much as we do. The Tories do it, and that's part of why they have a much more friendly media atmosphere than we do.
Take the Andrew Neil interview farce for example, people called Johnson dodging the interview cowardice, but he was 100% correct to realise that there was no upside for him, so why do it? The next Labour leader should flatly refuse, they should say "Andrew Neil is a right wing political activist who publishes a racist magazine and has ties to the anti-Semitic government of Hungary, I refuse to be interviewed by him."