Borg / k8s / Docker are not the same thing. Borg is the predecessor of k8s, a serious tool for running production software. Docker is the predecessor of Podman. They all use containers, but Borg / k8s manage complete software deployments (usually featuring processes running in containers) while Docker / Podman only run containers. Docker / Podman are better for development or small temporary deployments. Docker is a company that has moved features from their free software into paid software. Podman is run by RedHat.

There are a lot of publicly available container images out there, and most of them are poorly constructed, obsolete, unreprodicible, unverifiable, vulnerable software, uploaded by some random stranger who at one point wanted to host something.