The Pinephone by PINE64 and the Librem5 by Purism mark the dawn of mobile-desktop-convergence and GNU/Linux on mobile. I think Jami has the potential to become THE way to setup private communications on these platforms. I’ve tried out the GNOME application on mobian (mobile debian), and it works pretty well already. There are a handful of improvements that could be made to better account for touch screen controls.
It would be nice if the left panel with the conversations and contact search would tuck away to the left when a conversation is open. Maybe a simple edge swipe from the left to bring the contacts back. The settings GUI also tends to bunch up a little due to the tall aspect ratio of a phone, as well as the call controls. Video chat seems broken on Pinephone but that may not be an issue with the application itself.
A solid communications application like Jami would be a fantastic step forward in bringing mobile GNU/Linux into the fore. After all, the main purpose of a phone is communication.
Edit: Some GUI quirks in the Qt app here.