Responsive theme design for uSkinned Site Builder, a multiple award-winning package for Umbraco CMS.
Stroma Theme is an add-on package for uSkinned Site Builder. It is compatible with Umbraco (9, 10 +) and uSkinned Site Builder (2, 3 +).
https://our.umbraco.com/packages/starter-kits/uskinned-site-builder/
Please make sure you install uSkinned Site Builder before you install a theme.
How to get started
Step 1 — https://uskinned.net/support/how-to-install-umbraco-cms-and-uskinned-site-builder-from-nuget/
Step 2 — https://uskinned.net/support/how-to-download-and-install-a-uskinned-site-builder-theme-with-nuget/