Not great news if you use container Linux:

https://www.redhat.com/en/blog/faq-red-hat-acquire-coreos

Container Linux and its investment in container-optimized Linux and automated “over the air” software updates are complementary to Red Hat Enterprise Linux, Red Hat Enterprise Linux Atomic Host and Red Hat’s integrated container runtime and platform management capabilities. Red Hat Enterprise Linux’s content, the foundation of our application ecosystem will remain our only Linux offering. Whereas, some of the delivery mechanisms pioneered by Container Linux will be reviewed by a joint integration team and reconciled with Atomic.

Super disappointed in this part of it. Is anyone else aware/familiar with a decent immutable lightweight Linux distro like Container Linux?

If you're looking for immutability, I can recommend NixOS. However what is drawing me to container Linux is mainly its update process

The draw of CoreOS Linux for me is its curated pairing of the Linux kernel, Docker, and etcd. There was a commercial entity reviewing upstream changelogs and making sure that they were pairing components appropriately. I wonder if an non-commercial district can really get this right.

Take a look at Linuxkit by Docker: https://github.com/linuxkit/linuxkit . I didn't develop it, but I use it indirectly via Docker for Mac, which I use a lot. The latest version supports Kubernetes. This means Docker commercially maintains a Linux/Docker/Kubernetes stack that needs to run reliably on what I think is a very large install base. They have open-sourced the system they use for this, it's called Linuxkit and it's a very cool, underrated project.