Possibly, but downgrading from Android 9 to 8.1 (V31) may cause a bootloop. Check XDA for a "V31 Android 9 port".
or FactoryTool : Used to flash the .img file from a Windows PC. r329q v31 firmware upd download
While holding the button, connect the TV box to your PC using the USB cable. Possibly, but downgrading from Android 9 to 8
Open the device to confirm the PCB says "R329Q." r329q v31 firmware upd download