This link is nowhere in Gutenberg, nowhere in our wordpress.com testsite, nowhere in Jetpack, nowhere at Gutenstats.blog

Besides that the link does not explain the following questions:
Where exactly is the privacy policy at WordPress.com and Jetpack sites which tells users about this tracking?

Is this tracking opt-in or opt-out?

Where exactly can it be switched off?

What exactly else is tracked?
Maybe somebody else who is familiar with GDPR requirements can help with a more detailed answer. Thanks.