Using a local proxy is the right solution. ngrok didn’t work for me neither.
A similar tool that did work with facebook debugger is localtunnel ✅
npm install -g localtunnel
lt --port 8000
# or using npx without installing localtunnel
npx lt --port 8000
Generates a url that looks something like https://<random_hash>.localtunnel.me/. Using this url in facebook open graph debugger worked for me as of October 18th 2017. I only had to hit Fetch new scrape information button. 🍻
Cool thing about localtunnel is that you can easily host your own localtunnel server with github.com/localtunnel/server so if it ever stops working with localtunnel.me, you can run your own somewhere in the cloud ⛅