There has been a remote presentation of SimpleX Chat, its design and future development on Monerokon in June this year if you want some more details: https://mastodon.social/@simplex/110623729272875598

I'm personally using it since March / April this year and its development seems to be very focussed and it's becoming more and more stable. Also a desktop application which I have been missing very much since I'm not so keen to type longer conversations on a few inch touchscreen has been released for testing at least for Linux and Mac OS.