Up to a few days ago, the beta/preview Pages support for GraphQL for SP allowed to retrieve the content of a SP SitePage: Get a page in a site - Microsoft Graph beta | Microsoft Learn This feature apparently is no longer available - trying to expand to canvasLayout now returns an error and the documentation hasn't been updated to reflect the change.
Being able to retrieve the content of a SitePage seems such an elementary feature, we believe it should be available as it was or in a different form.