Drop unused 1bpp support from Stretch LCD code by JakubVanek · Pull Request #792 · ev3dev-lang-java/ev3dev-lang-java

Did you test the branch with the brick?

No, I don't currently have a free SD card (currently it is used by a non-robotic RPi, although I can reflash it later).

I think I remember that Jessie used 1bpp packed black and white bitmaps and Stretch used 32bpp XRGB8888 bitmaps. However, because the Jessie codepath somehow didn't work, the old LCD implementation was copied over untouched and the new code is used only on Stretch (and Buster nowadays).