[zeeya]

Yes. Ugoos locked the bootloader starting with that firmware version, and CoreELEC can't boot from SD Card on any device where the bootloader is locked.

Thanks for the quick response,

One more clarification please...

Can I independently update both firmwares? (Android & CoreELEC) or should I stick to the official only?
OR
Can I update CoreELEC on my own?

The dual boot firmware creates two separate partitions so independently updating shouldn't be a problem. I've done Android OTA updates & CoreELEC updates without any problem. I've not tried flashing Ugoos firmware as I mainly use CoreELEC, so can't confirm that, but OTA Android is fine.

You mean you are not using Ugoos stock firmware?