I'm confused, isn't Fedora Silverblue also image-based? I thought the default installation doesn't use layering, and that layering only comes when you want to install extra RPM packages.
Yes, Fedora Silverblue is image-based. We just use extending those stock images as an alternative to layering and easy way of shipping the same system configuration to many people.
An OCI image is pretty simple, yes, so is the sort of image that is in an OSTree repository. The difference is that when using `rpm-ostree` packages installed with `rpm-ostree install` are "layered" on top of the base image, while packages in the "base image" (be it OCI or OSTree) are part of the system and thus not "layered".
Adding packages in an image has the benefit of pseudo-reproducability (have the same image on multiple computers) and the added robustness of your base system being built elsewhere daily. Your computer just pulls the diffs. For example, there have been issues with rpmfusion on Fedora that ublue users completely avoided. Codecs & other essential rpmfusion packages are included in the images, and the rpmfusion repository is removed after they are installed. This way, if something package-related breaks it breaks at the image build stage, and an ordinary user wont even notice it before it is fixed.
The most noticeable benefit IMO, though, is being able to ship the same changes on top of a base image every day for multiple machines. This is not only packages, but for example udev rules, and other QoL things like our `justfile`s, configuration for https://just.systems/ that has some useful scripts for adding the kargs necesarry for Nvidia drivers to work and `just update` for updating the system, flatpaks & distroboxes.
