I decided to write a proper Arduino-library for the various Waveshare e-Ink – displays. I only have a 2.9′ black-and-white one and the 2.9′ red-black-and-white one, so I haven’t gotten to test the library on any of the other ones (donations welcome 😉 ) and the library is still under work, so there could be bugs and issues lying there, but so far it works fine on my ESP32. It’s pretty memory-hungry, so don’t expect it to work on e.g. Arduino Uno.
Just sharing in case anyone else has these displays and would like to play with them: