There's a signal text messaging application, there're a few 2 factor authentication applications, I don't know what anki is.
Hallium is an hardware enablement abstraction layer. We use it to port Ubuntu Touch and other OS, to devices that where built to run android.
We are not working towards android app emulation, we are working for running apps natively. We're doing this by using anbox, which basically is an minimal android image, with just enough to run apps, and that image is running inside an lxc container. However that is very hard to put it to work fully (access to sensors is one of the problems), and we have been asking for help with that.
Halium 'is the collaborative project to unify the Hardware Abstraction Layer for projects which run GNU/Linux on mobile devices with pre-installed Android' (https://halium.org/). The project to support Android apps is called Anbox but it's mostly on hold for now.
A few years ago I heard they were working towards android app emulation. Might have been called Halium?