In case anybody cares - I’m currently porting this one to run on a raspi pico W and making pretty good progress. It seems to be enough compute to do this job (and it’s an interesting adventure).
Note to others if you go down the ePaper path - waveshare sells two variants of their displays. One with a pi-compatible 40pin connector on the driver board, and a different pico-compatible variant that you just plug the pico into the back of. Pretty slick.
Their ‘universal driver board’ works with either if you figure out how to wire it up from the skeletal waveshare documentation. PM me if you need a nudge for wiring that works.
(minor update - porting the ‘data’ part to a pico was easy, but unfortunately the limited memory on the hardware prevents me from using the same framebuffer way to get the data onto the display, so I’m punting on this one. I did switch from a pi4 to a zeroW for the pi which works great FWIW.)