Proxies for Selenium
A real browser brings real constraints. Two of them surprise people every time.
Authentication
A username and password inside the address string is not accepted; the browser raises a dialog instead.
Either use an extension that supplies the credentials, or bind the authentication to your own address on the provider side so no credentials are needed.
The address is fixed for the session
Within a running browser the address does not change. Rotation means restarting, and that costs seconds every time.
Design the run around that: one address per session, sessions sized so restarts are rare.
Cut what you download
A full page load pulls images, fonts and third-party scripts. Switching them off removes up to two thirds of the traffic and speeds up every step.
One session, one identity
If the job involves signing in, keep the whole scenario on a single address from the first step to the last. A change mid-way closes the session.
options.add_argument(f"--proxy-server={PROXY}")
prefs = {"profile.managed_default_content_settings.images": 2}