This is the naive approach you would do 15+ years ago.

Then things got way better with real browser engines like Webkit that could understand Javascript. That was something that I've personally hacked together as a contractor for an anti-piracy customer using Python, Webkit and Qt framework (PyQt) in around 2009. Shortly after some nice libraries in node/js came out like Phantom.js which would make this much better.

If I were to do this today, I'd use Playwright.