Native app for UBports' Ubuntu Touch (16.04)
I dislike the way the other suggestion was laid out so here's a new one.
I would love to see a native ProtonMail app for Ubuntu Touch. The idea given in the other suggestion isn't enough as Libertine (the method to install desktop Debian apps) is broken on some devices. We need a native ProtonMail app for UBports' Ubuntu Touch 16.04. 15.04 is going to be deprecated soon.
Here is the other suggestion for an Ubuntu Touch app: