Attached is a zip file which will unzip into Marlin 2.0.7 modified for the stock AnyCubic delta Predator using the Chitu Trigorilla Pro 32 bit board and 3.5 inch touch screen. The firmware.bin file in the pio\build\trigorilla_pro folder should directly load onto the board, using a USB cable and the STMicro Demonstrator, if the board jumpers are correctly configured.
Alternatively, you can modify any files you need to, recompile under PlatformIO, and download your new firmware.bin file.
There is no need to physically rotate the display, and the only issue that I am seeing is that perhaps the filament detection logic is reversed. I am looking into that, but you can turn OFF filament detection from the touchscreen, and store that change, as a workaround.
The "Enter" and "Cancel" touch button positions will be swapped left to right, and the previously dark blue enter button will be an easier to see blue, but otherwise the functions are all "normal Marlin".
After updating your Predator to Marlin, you must run a delta calibration and save the changes from the touch screen.
The Marlin GitHub releases change too fast, and too far, especially in the realm of the user interface, for me to keep up with, so this will likely be my last post on this topic for quite a while. If I discover an improvement I'll post, otherwise I'm done for now.