I’m really worried with the Factory Installed eMMC Dual Boot.
Already identified by Portisch CE_STORAGE on your AM6 Ugoos is only about 1536MB
It’s not a correct official installation of CoreELEC.
If it was my hardware , I would flash their stock eMMC Android only image.
Then install CE to SD Card / USB and make sure it runs.
Then install the official method for CE dual boot eMMC