3.5 Firmware packaging and metadata
Visit the Nortek Software & Support Center to search for your specific model. Check for "Firmware" or "HDMI Update Tool" categories.
The open-source community has recently reverse-engineered the flashing protocol. There are now GitHub repositories hosting "unsigned" firmwares that unlock:
It looks like you’re looking for an related to the Nortek HD Box R1 and its HDMI firmware .
End of paper.