Hi Leo and thank you for your comments.

The nomacs package should probably go to gnu/packages/image-
> viewers.scm.
>
Yup.


> Use git-fetch instead and don't recurse into submodules.  You will
> likely encounter some errors, because it doesn't seem as though nomacs
> expects you to have its inputs properly packages.  *sigh*
>
Hmm, this one I'm not sure I understand the reasoning behind. I think I
read in some packaging guidelines that url-fetch was preferred if possible.


> Instead of adding the path to the source directory, try `(cd
> "ImageLounge")` in a phase after 'unpack.
>
I'm told that cd is an unbound variable when I try that :/

       #:phases (modify-phases %standard-phases
                  (add-after 'unpack 'cd-to-source-dir
                    (lambda _ (call-with-output-string (cd
"ImageLounge")))))

Try to sort them alphabetically, also don't put too much effort into
> making the tails align.
>
Check.

> One thing that's missing is the plugins that are developed in a
> > separate git repository [0] and not included in the source tarballs
> > of the main repository [1]. Ideas on how to make them available in
> > the `plugins` directory during build time are welcome.
> A trick that's often used in Guix is
> (inputs
>  `(("extra-source-package"
>     ,(origin ...)))
>    [other inputs])
> You can then (copy-recursively (assoc-ref inputs "extra-source-
> package") destination) in a phase between 'unpack and 'configure.
>
 Thank you! And thank you for the rest of the comments too.

Happy new year!