Hmm so you don't use rpm-ostree? Or ostree at all? Sorry I'm just having trouble finding some of the technical implementation details, seeing a lot of details on the UX though.

ostree is the library that rpm-ostree and bootc share. However bootc is moving over to composefs as a backend. This effectively makes it distro agnostic and there are communities forming: https://github.com/bootcrew

Fedora still uses rpm-ostree, when you do an update it's pulling from an ostree remote served from a server. bootc replaces that with just an OCI registry. We ship the `rpm-ostree` binary on the systems still. It's still used for things like adding kernel boot arguments.

Here's their diagram: https://bootc-dev.github.io/bootc/filesystem-storage.html

Generally speaking new users can skip the rpm-ostree parts and just start with bootc. I am not an expert in this, there's a rust library in there somewhere. Hopefully someone can help fill in the blanks.

Boots currently relies on OSTree, you use OSTree enable base images. But the work is well on its way to transition to composefs which uses kernel native tech to replicate the features need from OSTree, so any systemd enabled distro can become bootc-able, for a bunch of example see: https://github.com/bootcrew