This is a good example of a package/module that should be distributed
externally (e.g. as a flake [1]): it's not stable yet so anybody who
seriously wants to use it will want to use the upstream repo. Also,
it's highly specialized so NixOS is not really the right place at the
moment (every NixOS module slows down NixOS evaluation for everybody).
[1] https://github.com/edolstra/jormungandr/tree/flake
aa98348f88