@davew missed the question because $algorithm = false, but I’d respond Mastodon (and of course that’s also a self-fulfilling prophecy of an answer). Threads would be a grudging second. I generally see really strong engagement here. Next to zero engagement on Bluesky for me, so not a lot of stickiness. YMMV, my 2c. Also a big fan of e.g. the WordPress integration with the Fediverse -> your textcasting concept.