I have spent far, far too long messing about trying to get the 3D printed mounts for the trackball and keyboard, well mostly the keyboard, working to my satisfaction.
The keyboard has a kind of rounded kidney shape to it and I don't have the modelling skills to model it exactly so I've done a lot of tweak, print, repeat today.
Also, I seemed to kill the cheap clone Leonardo board I was testing with so had to dig out and solder up the headers on another. Obviously not before I wasted time wondering what was wrong. They're tough and 5V tolerant so no idea how I killed it.
Also I faffed with the idea of using a different Android phone than originally planned as it's much smaller but it only runs Android 6, which is frankly way too old and won't handle Termux.
Note to self: Do not get involved in trying to install LineageOS on the Moto G4+, it needs to stay working.