After downloading Manjaro Sway from repositorio oficial, I only managed to install Manjaro on SD and USB stick.
And I can’t find any official method to install in the emmc.
Unfortunately during installation, it doesn’t ask where you want to install it and it installs to the ISO boot location.
Hi,
You can flash the image with balena-etcher available with the aur packages…
more details here to build and flash your images 
Once you have it on SD card, you can install manjaro-arm-installer and use that to install it to emmc.
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