@Giuliano De Luca Thanks for making the detailed video on this topic. I have wrote the blog on similar topic a year ago.
In case if anyone like to follow the steps by reading the blog, here's the link to my blog: SharePoint Online: Create a blank page without header & title
Please click Mark as Best Response & Like if my post helped you to solve your issue. This will help others to find the correct solution easily. It also closes the item. If the post was useful in other ways, please consider giving it Like.