make a backup of your stock firmware using dd or the "Backup" tab in PhoenixSuit before trying any custom ROM.
To help find or configure the perfect software for your specific device, tell me:
Boot H6 into FEL (hold FEL button, power on), then:
Ensure your TV box is completely unplugged from its power adapter and your TV.
Installing a custom ROM on an Allwinner H6 device requires some technical knowledge and careful preparation: