Where did the option go to edit the HTML of a page?

The option to edit the HTML of a page isn’t there anymore ?

Omeka v4.0.1

In cases like this it’s always good to look at recently installed (or updated) modules. In this case, it turned out to be the Data Type RDF module (v 3.4.6) which brings in a version of the CKE Editor with a different configuration, at least sourcedialog plugin isn’t included or enabled.

For now I’ve disabled the module so I can edit the HTML source code (‘Broncode’ in Dutch):