Retroflag provides 2 device tree binary overlay files and a config.txt. They are necessary for getting the video and audio to work in the GPi case.
I looked into the provided dtbo files and managed to recreate source files for them.
- Run
compile-dts.shto get the.dtbofiles - Place the
.dtbofiles in/boot/overlays/ - Place the
config.txtfile in/boot/after backing up the stock config.txt
- Restore the stock
config.txtfrom backup