Legacy Dynamic Views are deprecated and USM replaces them.
That said, the old legacy dashboards if present are migrated when you upgrade so they are still viewable and can be opened in the new dashboard portlet. They may require some reconfiguration and they do not include the navigation window that used to be present on the left side of the Dynamic Views page/window.
Training Video for the new Dashboard (HTML5) portlet can be found at:
See also: "Getting Started with Dashboards" at:
keywords: how to create define new dashboards dashboard HTML HTML5 dynamic views custom