I am also unsure how buildx works, however I do know that the official docker build-and-push action is not compatible with podman (despite the podman-docker pkg), solely because it uses buildx. As well, compared to buildah builds, building with buildx is much faster--at least with default flags for buildah-build-and-push vs docker-build-and-push. I can say that buildx has an additional cache that must be cleared overtime, which might be related to the build speed difference.