I tested your kernel, but I still have a green screen
Like you said for testing I'm using an old ACER tv monitor probably with some bugs.
I did some more tests using a different monitor (a new LG TV) and the results are the same: green screen.
Also your suggestion to add
on the extlinux.conf is not working anymore (maybe the difference is the new build)
I can add that if I boot the stock android or LE 9.2 from SD everything works correctly, using the same cable and monitor