Customers who want to use a container to run osbuild need to follow specific steps such as running the container in privileged mode. Since this is possible, It would be beneficial if we had a premade image already configured to go. There are steps here https://github.com/osbuild/osbuild-composer-container#internals for setting up an osbuild container.
https://github.com/osbuild/osbuild-composer-container is a purely experimental project for now. Even though we are aware of usecases in which building an image in a privileged container seems to work fine, it's definitely not something that we are currently ready to commit to nor support it. Specifically for edge images: I believe that RHEL 9 edge images are built with LVM by default. Osbuild currently cannot handle LVM correctly in a container due to inability to configure the host's udev. While you might see an occasional success, there are known race conditions. I'm afraid that in the current state, we can only improve the documentation that running osbuild in a container is not supported and discouraged. Would it help?