Theme Builder Templates - kary4/divituts GitHub Wiki
In summary, header and footer are replaced as a pair due to technical limitations. If child themes want to display their own header/footer when either one is not overridden in TB they have to use the new hooks for this or replace the new theme-*.php template files. https://gist.github.com/atanas-dev/692be85eb77b9a7ca6b7ab6b266facf6
https://www.elegantthemes.com/documentation/developers/hooks/divi-template-hooks/