Possibly https://buildah.io/ would be of interest.

I do use podman, not really stoked about buildah because it's still a bunch of buildah commands in a shell-driven DSL, which I suppose is better than a dockerfile. Singularity was literally a build file that was a shell script divided into sections that denoted phases.

Bit late now but you could probably make something like it using buildkit - https://github.com/moby/buildkit/blob/master/examples/buildk...