I think you are confusing two things.
A. How the GitHub platform works
B. What a GitHub Action is
While it is useful to know about A.,
I am more interested in B., and having GitHub Actions implemented for podman.
In my initial e-mail, I posted links to various GitHub Actions which are implemented
in GitHub Repositories. These Actions can be used to do various things like
install docker toolchains, build containers, and push containers to registries,
all using GitHub runner infrastructure.
The actual implementation of these GitHub Actions is done in various languages.
For example, https://github.com/docker/build-push-action
Actions implemented in the https://github.com/docker
organization are implemented by Docker (the company),
so it is unlikely that they would be interested in adding podman support to these Actions.
If there were a set of equivalent GitHub Actions implemented in the https://github.com/containers
that worked with podman/buildah, that might be interesting to have.