My current plan is to visit southern Quebec this September. I plan to leave Burlington, Vermont and head north, through the islands. After crossing at Noyan, I'll follow 223 up through St. Jean Sur Richelieu and Chambly, up to pick up Veloroute 3 at Sorel-Tracy. Thus avoiding the suburbs around Montreal. Then, I'll follow that to Lévis and take the ferry to Quebec City. After a short stay there, my plan is to take the ferry back and follow Veloroute 1 through Victoriaville, Sherbrooke, Magog, Granby, etc. back to St. Jean Sur Richelieu.
My usual mode is camping in the country and hotels/motels/hostels in cities.
Any suggestions as to route modification, must sees, must misses will be gratefully received.
Thank you and Merci in advance.

In case you haven't yet seen this website containing all major bike paths in Quebec :
https://www.routeverte.com/cartographie-route-verte/

Some towns and cities have their own local bike path maps if you look on their websites.

Example of the above map with your intended direction :

Nice, thank you.
One little problem I have is the Cycling Quebec atlas of Veloroutes doesn't have regular roads, and my Quebec Atlas des Routes Secondaires doesn't have veloroutes. Do you know of a publication with both?

I've never heard of a "Cycling Quebec atlas of Veloroutes" and searching for it only brings up your post.
I'm not familiar with what is available as far as guides go as I haven't yet done enough touring to need them.

My typo! Cycling in Quebec is the atlas of La Route Verte, published by Velo Quebec.

Odd that the book (which I haven't seen) doesn't include normal roads.
The online interactive map does.