This app was mentioned in 1 comment, with an average of 2.00 upvotes
Thanks! I just found that "Canoe France" site you linked has a really quite good app, Here; It made it very easy to see on a map where everything is, the date the season opens (most seem not until April), and helped see what self-guided trips are available...
...though I still can't make up my mind on a river, so many good options!