There is an unofficial one for Mac (i.e. not actively developed and anyway not by the core devs) - Seaglass. Pretty much dead/abandoned.

Besides, irrespective of what the founder (or someone) might say/indicate at times I really don't think Matrix/Riot is looking to compete with Telegram/WhatsApp/Signal. They are trying for a pie of what Slack and the kind have. I am giving up on Matrix as well for it to ever be a personal IM app/service. It' just doesn't make sense and biggest reason for that not happening are:

- People are not going to bother finding different instances, or host their own - they just want one service, one server

- The UI of Riot is specifically designed for group/team chats and I don't think they will try to stand in two boats in one app or have two separate apps.

- There's no money in personal IM apps. So unless there's a coffer like Fb/Telegram or someone like Acton donates handsomely at some point there isn't much there other than just being another Diaspora but in instant messaging space.