If I specify: parts:   foo:     build-packages:     - on arm64: ["bar:armhf"] then the build will fail in LP with something like: Using 'snapcraft.yaml': Project assets will be searched for from the 'snap' directory. Could not find a required package in 'build-packages': foo:armhf Build failed This is because the LP chroot for arm64 by design doesn't have foreign architecture support and there are no armhf lines configured in sources.list. I would expect that specifying "foo:i386" would update the build environment as necessary on amd64 so the package is installable, and the same for "foo:armhf" with arm64. This would be useful for stage-packages as well. I ran into this because I was trying to build some binaries with -m32 on arm64 and needed gcc-multilib. gcc-multilib is only available in the Ubuntu archive with "gcc-multilib:armhf", but this fails to install in LP using its arm64 chroot.