Upgrading the firmware on a Sunplus-based Android TV box typically involves either a simple online update through the device settings or a manual flash using a USB drive if the system is unresponsive. Firmware Upgrade Report: Sunplus Box TV1 20

Use this if the device is totally dead (bricked) or you are downgrading.

I can provide the exact file names and remote button shortcuts for your specific hardware configuration. Share public link

Use this if your box is working normally and you just want to update.