Hello and welcome to the forum,
Sorry for not reading your post earlier as I have missed many post lately.
Currently you can run Manjaro from SD Card when you have android installed in your emmc, Using the existing uboot in emmc you can just flash manjaro on emmc which will still use android uboot on emmc while running manjaro from the emmc too.
This can be achieved by running a script which in install the boot directory. file name is
Try the following steps:
Step 1: Flash Latest Android on Emmc using their burning tool.
Step 2: Flash Latest Manjaro Vim3 image on sd card and rename
u-boot.extinside boot partition called
Step 3: Enable Multi-Boot by pressing Function key 3 times while sd card is inserted. This will boot into Manjaro on sd card.
Step 4: Test if everything is working on it and then Upgrade to latest packages using Pamac Software update or command line
sudo pacman -Syyu
Step 5: Run install script
Step 6 : Reboot system with sd card inserted and follow step 3 again and once you see Manjaro on SD is booting fine then try to reboot with sd card removed and this time it will boot into Manjaro over emmc.
This is a bit confusing but that is one of the ways to get Manjaro on Amlogic Soc. We do not maintain uboot for Vim3 yet as it is still not flexible to use it with any other uboot on emmc.
U-boot = BIOS of ARM hardware
No, they have old libraries which are needed or maybe they can do it with Mainline uboot and Mainline kernel as they do with their 5.7 image, but as they don't push their work to ubuntu upstream repo it might keep breaking the system on updates.
You don't need this as our kernel update doesnt break the uboot as we maintain our kernel and push it to the repo while they dont push it to the repo and instead they build new images with updated kernel regularly.
I have my vim3 working on Manjaro over eMMC and I have had it installed when we were on 5.3 and now we have 5.7.8 and it never break anything so far.
Try the steps and see if that is what you were looking for. Make sure you follow the steps accurately as if you miss anything from it then it will soft-■■■■■ your device and you will have to start again from step one.