This was answered here: F41 Kinoite Native Container - DNF5 PGP key import error - #3 by siosm
For now, rpm-ostree is still the way to do layering. There is a longstanding effort for dnf + ostree integration, but we’re not there yet.
What’s new (and emerging!) is using dnf + bootc to make custom bootable images - Getting Started with Bootable Containers :: Fedora Docs