Not sure why the "Avoid Motorways" option seems to plague a lot of sat navs. My TomTom does what you ask of it (for the most part) but the one I use for biking which is MS Maps when set to Avoid Motorways also includes A roads which is a bit of a chit as it sometimes says cannot set route as no roads exist to destination, so I have to have Motorways enabled and use the grey matter to avoid them and let the sat nav recalculate which it finally does after trying a 1001 times to get me to do a U turn. I did try using paper maps but they keep blowing off the tank !
I think that Beeline is the one TMF has and did a feature on
