> +  (let ((commit "87f78ab3d7ed0dedf56edc38242d559ac07b1330")
> +        (revision "1"))
> +    (package
> +      (name "qalculate-gtk")
> +      (version (git-version "3.8.0" revision commit))

Same as in libqalculate, please use the git tag "v3.8.0" instead.

> +         ("automake" ,automake)
> +         ("autoconf" ,autoconf)

Why?

> +           (add-before 'check 'update-po-files ;; to pass po check

Please use just one semicolon for this kind of comment.
Maybe also include the error message one would get otherwise, as a comment.

> +             (lambda _
> +               (with-output-to-file "po/POTFILES.skip"
> +                 (lambda _ (format #t "data/shortcuts.ui~%"))))))))

Please end the phase in #t.