If the site is not drupal 9 compatible by 2 of November, what will happen exactly?
From what I understood, the site will be available only inside the CERN network (which means it will not be available to the public), right?
For our site, it’s important that it remains available to the public.
My team needs to prioritize the tasks.
Your understanding is correct. This is not something which will happen at midnight the 2nd of November, but it goes without saying that the longer a website remains on Drupal 8, the greater the security risk it is exposed to. It is for this reason that such sites will eventually be made inaccessible to the general public. With that said, in practice, your website will continue to work the 2nd of November. Please rest assured that we will not upgrade any site which is not compatible. We will be reaching out to website owners still on Drupal 8 and do our best to help you upgrade accordingly.