I have a website where since 2 weeks there were some problems with CLS. https://developers.google.com/speed/pagespeed/insights/?hl=IT&url=https%3A%2F%2Fwww.notizieoggi24.it%2F2020%2F10%2F01%2Fspread-btp-bund-oggi-1-ottobre-apertura-in-calo%2F
Site is some fast, but only CLS have problem. I don't know what is the problem. Maybe font?
I have "CSS above the fold" with Critical CSS, but also with raw CSS I have the same result with CLS.
Use the lighthouse tool that is part of developer tools instead (Chrome browser) Then you can view whole of the original trace (frame by frame)
On the trace page, click experience, then the event log tab. That will give you a break down of all the layout shifts.
From experience, it's usually images with no sizes, fonts loading late or cookie consent banners.
Another tip is to use dev tools, then switch to mobile view and you can simulate a slow internet connection, then you can see if things move around when the page loads