To build one of the recipes simply use debos recipe.yml
Both, the mainline and the halium recipe, support installing Plasma Mobile in the image. You can build the Plasma Mobile variant like this:
debos --memory=4G --scratchsize=8G -t variant:plasma-mobile recipe.yml"
The images can be built for different architectures
debos --memory=4G --scratchsize=8G -t architecture:arm64