I also did something similar for my spring project. The idea was to buy a used car and I was frustrated with the BS the listing sites claimed as fair price etc..

I went the browser extension route and used grease monkey to inject custom JavaScript. I patched the window.fetch and because it was a react page it did most of the work for me providing me with a slightly convolute JSON doc everytime I scrolled. Getting the data extracted was only a question of getting a flask API with correct CORS settings running.

Thanks for posting using a local proxy for even more control could be helpful in the future.