In the Plan mode of the board, when you select an Epic or a Version, the backlog and sprints correctly hide issues that don’t belong to the selected Epic or Version. However, if a Sprint has no issues, it is still displayed and greyed out.

It would be useful if, when an Epic or Version is selected, Sprints that don’t contain any issues (or any issues associated with the selected Epic or Version) were hidden entirely instead of being greyed out.