One way I did this randomly the other day was choosing Bicycle or Walking mode which prioritize slow streets and pedestrian pathways. Maybe a different definition of thrilling than most people in cars, but I appreciate being taken into other areas of town I might not normally go since they're not major roads.
OsmAnd also has many different navigation profile options, you might try customizing that to get what you want. Organic Maps focuses on what the bulk of people need to navigate decently, so that the end result is simple and usable for everyone even if it's not the most feature-packed.
Feature Request: Add a Thrilling style mode for navigation so I can map fun drives without using a real computer. https://help.tomtom.com/hc/en-us/articles/10428741608466-Rou...
Here is more information about the variables they use to figure out the most thrilling route -- https://developer.tomtom.com/blog/build-different/thrills-an...