I posted previously about some display flickering, and I was having trouble getting the UART connection between the Pico and the Pi 3a working.  With Ubuntu on the Pi 3, when I had the UART wires connected, the system would flash the display and not boot.  I changed the OS to Raspberry Pi OS and it would boot normally, but I couldn't receive anything from the Pico.  I kind of got frustrated with this and took a few weeks off from working on it.  

I explored the idea of using I2C instead of UART, but I2C slave functionality isn't really supported by MicroPython.  I talked to my guru a bit and troubleshooted by hooking up a USB UART thing to each device separately and found that the pi 3 was working normally but the Pico had no TX!

I was able to move the wires that were controlling the system power and pi LiPo shim and free up an alternate set of UART pins and everything is working now!!  A basic keymap and it's printing some characters on the screen.   

This is where I'm at now.  

• I need to develop the keymap - The front keyboard is from a prev build, and I added the back 5-way switches because it sucks using only thumbs, so I can use the back switches for arrow keys, mouse wheel, and ctrl alt shift stuff, among other stuff that reduces load on the thumbs.
• clean up the keeb firmware to work better with this system - e.g. adding hold-shift support.  I've only used oneshot shift on prev builds. 
• Add some of the power stuff - flash display on low battery, auto shutdown, and full power off on battery limit.  
• And playing with stuff!  Gonna try the beeper matrix client and tweak some stuff for a nice tmux experience.  I'm excited about trying carbonyl (fast chromium based terminal browser).  And there's a bunch of other terminal stuff to play with.