I use a a very means to test and adjust my router to get the spindle perpendicular to the spoil board. It takes about 3 minutes to make it. I have used one for years and it works well.
Bend a 8-10 inch long piece of brass or steel rod into a ‘Z’ shape leaving about 1/2 inch on each end.
Clamp the rod in your router’s collet (be sure to unplug your router, you do not want to turn it on)
Lower your ‘z’ axis until the free end of the tool just touches the waste board.
Rotate the spindle/collet and the tool will show how far off perpendicular your spindle is.