Monocles chat is best one for Android, it is the most complete chatting app for todays standards, unlike Conversations it has swipe to reply, last seen, emoji reactions etc. The only issue is making account there, need to use other homeserver like @conversations.im if you don't want to pay for their @monocles.eu . For IOS the only option is Monal. For web I find conversejs better than mov.im as movim doesn't encrypt sent pictures in chat at all, and encryption of text messages is sometimes broken depending on how you set it up in settings of account and in chat, as it needs to be activated on both places, so conversejs is better, but less enjoyable UI than movim