Yeah, the units shipping with 4.21 can’t use any of the custom firmwares because these dsos now use a different lcd driver. That’s why we get the white screen of death. Apparently the original lcds are out of production.
It doesn’t look like this new firmware with the updated lcd drivers are open source either, complicating the matter of porting the drivers to benf. Still, I’m keeping my fingers crossed that someone smart can figure it out.