Tried it a few more times and it worked !!!. I run American Megatrends AMI BIOS, Aptio V2.13. The trick that worked for me is to set:
- Legacy USB support to Enabled
- USB device power up delay to 5s
- USB the be seen as Hard Disk (USB, Mass Storage Devices - Hard Disk)
- Boot order needs to be set in two places; Main menu of Boot options where you set the order of devices: USB, Hard Disk . But since we have set the USB to be recognized as Hard Disk, you also need to set the order in which Hard Disks are booted. There is a line below, something like HDD Boot order. Here you have to set the USB Hard disk to have priority over built in SATA disk.
Took me a week, but finally I managed to upgrade to latest LibreELEC.
Thank you.