Upgrading the bootloader [WeTEK Play OpenELEC edition]

Hello.

I have a WeTEK Play (OpenELEC edition). I upgraded it to LibreELEC stable (7.0.2) from original OpenELEC some months ago, using the standard procedure of putting a file in the .update folder of my internal NAND. It works perfectly.

I would like to test the newer LibreELEC alpha versions booting from my mSD card, and I have not been able to do it until now. Every time I put an SD with an alpha LibreELEC version (created with dd or LibreELEC SD Creator) I can see the splash screen of LibreELEC-alpha, but it finally boots to my stable version in the internal NAND.

I have googled a bit and found this: Boot from mSD on WeTeK OpenELEC Edition not working · Issue #4550 · OpenELEC/OpenELEC.tv · GitHub (it is for OpenELEC, but I think it doesn't matter, it's the same in LibreELEC).

So, it seems that upgrading the bootloader fixes the problem: Update WeTek Play bootloader by codesnake · Pull Request #4628 · OpenELEC/OpenELEC.tv · GitHub

The question is: how can I upgrade my bootloader without touching the rest of my NAND installation? Is this possible?

Thanks in advanced.

Quote from codesnake

Make a backup, do clean install of LE 7.0.2 into NAND via recovery, restore the backup.

Yes, that's what I did. I only wanted to avoid backing up/restoring my NAND. I thought it was possible to upgrade the bootloader from LibreELEC (using something like nandwrite).

Now I can boot newer versions of LibreELEC from my mSD.

Thanks.