Comment by Arathorn

Matrix is pretty simple too; one HTTP hit to send a message; one HTTP hit to receive a message. c.f. https://news.ycombinator.com/item?id=20949477

As others have pointed out, there's also a pretty decent range of very usable "daily driver" clients these days (Element, weechat, FluffyChat, nheko, Quaternion, NeoChat all spring to mind). 2nd generation servers are also progressing well (Dendrite in Go & Conduit in Rust).