Quoting from DOE’s announcement:

The U.S. Department of Energy (DOE) Office of Science (SC) today announces the selection of six collaborations focused on leadership in scientific-software sustainability. These collaborations will explore innovative approaches to the stewardship and improvement of the software ecosystem for high-performance and scientific computing, including the software ecosystem developed through the Exascale Computing Project (ECP), in order that the full potential of the current and future computing systems deployed by DOE can be continuously realized. The software ecosystem provides shared software packages, novel evaluation systems, and applications relevant to the science and engineering requirements of DOE.

SC’s Advanced Scientific Computing Research (ASCR) program looks forward to working with these teams, and our entire community, to chart a path forward for leadership in scientific-software sustainability.

You can read the funded proposal. Though the proposal is technically for the planning phase, our SSO concept is described well there.