Best Tool to Establish Core Web Vitals Baseline's

What does r/SEO think is the best and most reliable source of information regarding the upcoming Core Web Vitals update that is rolling out in the next few months? Go straight to the source and use GSC/Lighthouse to establish baselines? Or go to a 3rd party source like GTmetrix?

Just want to make sure that I am looking at the most reliable information so that I can best communicate with our web dev team on what to attack