siteorigin-panels

SiteOrigin Page Builder is a powerful content creation interface, instantly recognizable, astonishingly different. SiteOrigin Page Builder makes it easy to create responsive column-based content using the widgets you know and love. Your content will accurately adapt to all mobile devices, ensuring your site is mobile-ready. Maintained by siteorigin on GitHub, where it has earned 617 stars from the community.

It's actively developed around block-editor, page-builder, siteorigin, and is a solid reference for anyone building with these tools.