Bruce.Qin - I have updated both the BIOS and EC to the 4/16/2021 released versions.
Using an EFI version of OpenWRT 19.07.5 image, I first tested from a USB thumb drive and the USB was seen as a EFI device and booted without issue.
I next tried the same image on the eMMC storage. I used a bootable UBS version of FINNIX and completed the following steps
wget https://github.com/oofnikj/openwrt-efi-tools/releases/download/v19.07.5/openwrt-19.07.5-x86-64-combined-ext4-efi-resized.img.gz
gzip -d openwrt-19.07.5-x86-64-combined-ext4-efi-resized.img.gz
dd if=openwrt-19.07.5-x86-64-combined-ext4-efi-resized.img of=/dev/mmcblk0
There were no errors during this process. After reboot, the eMMC was not recognized as an EFI boot option in the BIOS setup.
So I am still unable to install and boot from the eMMC storage on the ODYSSEY X86J4104864 onboard storage.