I guess this thread has inadvertently been kissed out of a deep sleep. But regarding the question of the original topic poster, if there is an interest in a single/double track on dirt east of Quebec-City, I can recommend the former Monk railway line, now a rail-trail. See
https://ridewithgps.com/routes/28916123 . I hit upon it by chance, a recommendation of a local snowmobile rider. I hadn't seen it on the OSM-cycle maps of the region. From near Quebec-City you can follow it up to Pohenegamook, the most northern point of the lower 48 US-states. I rode it in reverse direction from near Poheneganook to Sainte-Perpetue. It was mostly in very good condition.