

UBlue is a tool the fedora team created to build immutable distros in a container. This is a list of official distros created by it. If you’ve seen Bazzite it was also created with UBlue.
Immutable distro just means the root filesystem is mounted read-only. So when you do updates, they create another image of your filesystem with the updates applied. Then you have to boot into the new filesystem. This is called an atomic upgrade. So if something is broken, you reload your last image and everything is fine.
May, I introduce you to bedrock