why don’t you compare the crawler view from your flarum site with that of your discourse site? Use curl and the google user agent, for example.
Pick a couple of views, e.g. topic list and a topic, then copy the html of both into a Chatbot and ask the AI to compare the html of both.
You may need to bring your flarum site back up to do this comparison if you have switched it off. Just put it temporarily on a subdomain - e.g. flarum.