Fedora has its own mkinitrd(8) that conflicts with the Sortix one. Add instructions to cross-development(7) for what to do. Potentially rename the program, but that will have to happen after the 1.1 release due to build tool stability requirements. If so, the 1.1 release would have to be forward compatible with the new scheme. Maybe let people install it by another name and then set MKINITRD? Alternatively, the program could be a targeted tool, so i686-sortix-mkinitrd and x86_64-sortix-mkinitrd would get installed. Alternatively a wrapper program could detect the presence of the --format option and decide whether to run the distro version or not. Alternatively people can be required to keep both in the PATH, letting the Sortix one win. This is an unfortunate situation.
Marking as release-blocking because a decision must be taken prior to the release if a future compatible scheme is selected.