I've used apps like AllTrails and they occasionally have data on international routes.

My best advice would be to ask locals if you can (could include hotel concierge, airbnb hosts, etc.). Do that well in advance though and while you're planning, for your own safety! I'm always hesitant to let people I don't know know what unfamiliar ground I'll be stomping around. I usually ask for a list. 

Anyone who has actually done a route will be 100x more valuable than relying on random info you might find which could be outdated, subjective, or (my least favorite) marketing.