How does Cloudflare differentiate Selenium and Requests traffic?
The captcha response depends on the browser fingerprint. It's not about just sending Cookies and User-agent.
Copy all the headers from Network Tab in Developers console, and send all the key value pairs as headers in request library.
This method should work logically.
There are additional JavaScript APIs exposed to the webpage when using Selenium. If you can disable them, you may be able to fix the problem.
Cloudflare doesn't only check HTTP headers or javascript — it also analyses the TLS header. I'm not sure exactly how it does it, but I've found that it can be circumvented by using NSS instead of OpenSSL (though it's not well integrated into Requests).