When it’s the device with S905X it should work with correct DTB. You can try edit config.ini and on the end uncomment the line coreelec= and modify it to coreelec='nopkmute debugging'. Then you might can see some prints on the screen and maybe the reason.
And such old devices do need minimum Android 7.1 installed!
You could try alternative ROMS like ATV Experience, AidanTVROM etc. - search the forum and you’'l get some hints. Burn the ROM and keep only the bootloader for CE on internal instalation.