"Scrum is a framework" immediately follows the "What is Scrum?" heading on https://www.scrumguides.org/ also Jim Coplien directly told me the point of the Scrum framework is to design your own process.
Regarding Kanban - I'm talking about the Kanban used in software development as defined by David J. Anderson and not the token used in manufacturing by Toyota and DJA himself previously wrote "Kanban is not a software development lifecycle methodology or an approach to project management. It requires that some process is already in place so that Kanban can be applied to incrementally change the underlying process." and "Kanban is a change-management technique that requires making alterations to an existing process".