How do I check my broadband speed and report a fault through my ISP's online account portal?

My home internet has been noticeably slower for the past week. Before phoning my broadband provider, I want to use their online account area to run their official speed test and log a fault so there's a record of it.

How to navigate a typical ISP account portal to find service status, run the provider's own line test, and raise a fault ticket.

I can log in to my provider's website, but the account area is mostly bills and upgrade offers. I can't find anything about line checks or faults — the Help link just takes me to generic articles and a chatbot that keeps suggesting I restart my router.