Comment by marcthe12

Well flatpak was started pre oci. But its core is is just ostree + bwrap. Bwrap does the sandboxing and ostree handles the storage and mount. Now there still a few more stuff but these 2 are the equivalent to docker. Bwrap is also used for steam and some other sandboxing usecases. Ostree is the core of fedora silverblue. Runtimes are special distros in a way, but since the official one are pretty building everything from source so the repos tend to be messy with buildscripts for everything.