Nice Work! It took me al lot of time in parallel search on other items (Octoptint, motion, update, reconfig,memorycard crashing .. and again...), but the Display ist working (mostly).
I never would have get in run without your work in this thread.
Is there additional documentation about the framebuffer-device? There is a big vertical line on one side of the display. When the OPI is not running its perfectly white/grey and while init it's ok - but when ready. I am missing 3cm...