Speaking as a Solus team member, and KDE contributor:
Since this widget is already provided by the "Get New" mechanism in the Widgets UI, that's the way it should be installed. It would be inadvisable for us to package it, and stretch our package maintainers even thinner.
It is not recommended that people install this from the GitHub repo, KDE New Stuff (a.k.a. Get New) is the supported way of installing widgets that are available through it.