When you open the Dev tools (F12) you need to go to the performance tab.
Then you need to click on the record button (grey dot, upper left corner). It is recording the performance session now, including the user experience. So now you need to reload the webpage and after that stop recording. Now you can see all the data you need.
But for my own website, I did some tweaking and the screen rendering is now at once, with a minimum layout shifting. Now the CLS score is 0.02 or so, which is very good. But at the same time, the first paint time, loading time, is now longer than before.
