bootc and OSTree are both very neat, but the bleeding edge of immutable Linux distros (GNOME OS, KDE Linux) is currently converging on a different proposal by systemd developers that's standardized by the UAPI Group (https://uapi-group.org/specifications/). It fixes quite a few of the complexities with OSTree (updates are handled by `systemd-sysupdate`/`updatectl` and are just files served via HTTP) and is quite a bit easier to extend with things like an immutable version of the Nvidia drivers or codecs thanks to system extensions handled by `systemd-sysext` (which in turn are just simple squashfs files overlayed over `/usr`) and configuration via `systemd-confext`. `mkosi`, also by systemd, is quickly becoming _the_ way to build custom images too, and is somewhat tied to these new standards.
These are words but they don't make sense.
> Contributing members include people from Ubuntu Core, Debian, GNOME OS, Fedora CoreOS, Endless OS, Arch Linux, SUSE, Flatcar, systemd, image-builder/osbuild, mkosi, tpm2-software, System Transparency, buildstream, BTRFS, bootc, composefs, (rpm-)ostree, Microsoft, Amazon, and Meta.
Note systemd, (rpm-)ostree and bootc.
My understanding is that uapi is another initiative but not completely separated from bootc and ostree. Maybe complementary.
Next up, backups stored as layers in the same OCI registries.
I am not, however, sure ostree is going to be the final image format. Last time I looked work was in progress to replace that.
https://github.com/bootc-dev/bootc/issues/1190
There's a GitHub org that builds bootc-ready images for non-Red Hat family distributions using this backend.
https://github.com/bootcrew