As the name suggests, the fix consists in kernel config and DT changes, in order to enable DP out through USB-C, and eDP, in NanoPC-T4 legacy. It can run dual displays.
I was able to test USB-C DP, but not eDP since I don’t own a screen.
3D acceleration works like a charm in both displays
(The apparent glitch is because when you touch the right edge of the first screen, the windows resizes for an instant to fill the right half)