Dual Boot SDCARD and eMMC

Hello I see some boards using RK3399 being able to boot either on SDcard and eMMC by pressing a button (BOOT pin is tied low during boot up).
I see that this is not enabled here. WHy is that so? or anyway to still dual boot?


if you have android in eMMC, and write linux image to uSD card, plug uSD card and power on, rock960 should boot from uSD card. If not, check if the uSD card image is writing ok. Plug the uSD card to a linux pc, it should show 5 partitions.