Mastodon

Mastodon's defining choice is the strictly chronological timeline. No ranking, no For You, no injected suggestions; you see exactly the posts from people you follow, newest first, which is increasingly rare and the reason many people moved. Federation is the other half: you join one server among thousands, and your experience splits into a Home feed, a Local timeline of your server, and a Federated timeline of the wider network. That architecture is principled but front-loads confusion. New users must pick a server before they understand what servers are, and the local-versus-federated distinction has no analog in centralized apps. Content warnings are a first-class compose feature, collapsing flagged posts behind a tap. The interface is functional and uncluttered, but onboarding is genuinely the hardest part of the product.