I think the main problem is “link aggregator” which doesn’t make a lot of sense as the main function is discussion. For a minimal change you could go for “a discussion platform for the fediverse”.

If “fediverse” is too obscure; you could try just “a decentralised discussion platform”. Decentralised isn’t technical, you can’t fully describe the fediverse in a sentence but “decentralised” gives a clue.