It seems the Determinate Nix installer supports Fedora Atomic and SELinux.
On topic:
I really like Nix and home-manager. I’ve mostly switched to NixOS because it’s more convenient for window manager setups than building ublue images imo.
Having to mess with containers for different dev environments and keeping the up to date is imo more annoying than creating a shell.nix
Also being able manage my dorfiles with home-manager and installing software declaratively helps in keeping the system free of clutter.