Help booting from SD card

My manjaro on the internal emmc get corrupted at last upgrade because I found some errors (I don't remember the exact message) and now it stops after the kernel boot because it does not find a valid init.

So I put a new distribution on an external SD card but my pinebook still boots from the internal emmc: how can I force to boot from SD?

I think it must be cause of the sd card, can you try with some other sd card?

This thread from pine64 points out that mostly it is cause of the type of sd card.

Emergency solved: the internal emmc booted normally without any intervention and I don't need anymore to use the external SD.

But the question remains: there is no way to force a different boot device?

Thanks the same!

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