Related: A free guide on the usability of intranet design:

Intranet Portals: UX Design Experience from Real-Life Projects https://www.nngroup.com/reports/intranet-portals-experiences...

A small usability lapse: no publication date on the page, or in the report (presumably intentional). The report states:

"The research for this report was done in 2013, but the majority of the advice may still be applicable today, because people and principles of good design change much more slowly than computer technology does."