For me, Matrix (or I guess Element) really takes a long time to sync all my chatrooms when I login from a new browser. Not sure if it's just because the server I'm in is shit, and I'm leaning with that because I've been unable to use my Matrix for several days now due to the server itself being down even though the Element client is up (I guess u/emma is wondering now what happened with my testing of her new commits to an experimental branch of Postmill lol)