First, we need to resolve the HDMI issue you encountered due to changes in the booting file.
We have two options,
- Flash the latest image with updated u-boot so that you can directly accessthe u-boot console from HDMI0.
After doing this, let us know, we will guide you for applying custom overlays.
- For Debugging, if you do have a USB to UART Serial Module, then send us the log.
UART Serial Console