The right click context menu has an option to lock the viewport, but it does not work. The properties dialog is a better work-around than resorting to the command line which takes many steps [select viewport].  In either case since “cycle to select” functionality” is missing, the layer must be changed to something other than the viewport layer, then the viewports layer must be frozen, then lock setting changed(4 steps), then viewport layer has to be thawed. I attached a screen shot showing that the right click, context sensitive menu is not matching the properties dialog which shows the correct state of the setting.