These are the source Dockerfiles for the apax/vagrant-ubuntu docker images.
To build the Ubuntu 18.04 image for both arm and x86:
docker buildx build --push --platform linux/arm64,linux/amd64 -t apax/vagrant-ubuntu:18.04 -f Dockerfile.bionic .
To build the Ubuntu 20.04 image for both arm and x86:
docker buildx build --push --platform linux/arm64,linux/amd64 -t apax/vagrant-ubuntu:20.04 -f Dockerfile.focal .
To build the Ubuntu 22.04 image for both arm and x86:
docker buildx build --push --platform linux/arm64,linux/amd64 -t apax/vagrant-ubuntu:22.04 -f Dockerfile.jammy .