Demonstration of CSS-only grid with scrolling body and frozen header. It uses grid role for testing/demonstration purposes, despite currently having no interaction.
Two implementation details are worth noting: Edge does not support ARIA grid/table rows on semantic table elements, so all elements in this example are divs. Second, role="rowgroup" is not supported, so it has not been used.
See the Pen Scrolling grid by Sarah Higley (@smhigley) on CodePen.