Due to differences between Ragnarok and other OSes,
When booting you need to hold down the "SPI Recovery button",
For more info:
https://wiki.odroid.com/odroid_go_advance/application_note/forced_sd_boot
In future there will be mechanism for re-programming onboard SPI flash chip,
On first boot the device will create and re-size data partition,
and will shut itself off.
You need to power it up again for the time-being.