Tangential question, is there a canonical way to build cross-platform docker images without using docker hub? For example, armhf on an x86. I've seen some stuff

Tangential question, is there a canonical way to build cross-platform docker images without using docker hub? For example, armhf on an x86. I've seen some stuff from Balena, but nothing that looks particularly straight forward. Unless I misunderstand, docker cross is simply for cross compiling apps. I've been experimenting a lot with embedded boards and compiling a couple of large libraries on a Pi can take all night.