There's been a proposal for Fedora Linux to become a new Fedora immutable variant and now it's been approved by the Fedora Engineering and Steering Committee (FESCo) to happen for the Fedora 39 cycle.
While there is already Fedora Silverblue as a Fedora Workstation variant leveraging RPM-OSTree for creating an ummutable OS image and Fedora Kinoite as a KDE-based alternative, Fedora Onyx has been proposed as a new immutable variant of Fedora Linux.