Kalapress
Kalapress is our in-house Wordpress page builder. Its repo can be found here: https://github.com/kalamuna/kalapress-page-builder-plugin with the associated theme here: https://github.com/kalamuna/kalapress-theme
Other Options
Here are a collection of recommended page builders. When selecting a page builder, consider the objective of the content manager, and the types of tasks that they are projected to take on over the course of the project.
Page Builder Tier List
https://www.youtube.com/watch?v=Tkw7OgAilN4