CKEditor 5 does not support WYSIWG

Problem/Motivation

In CKEditor 4 content was rendered using the site's front-end theme, with some overrides from the ckeditor stylesheets. In any case, very little work was required to make the iframe preview in the editor WYSIWYG.

In CKEditor 5 there is still the possibility to provide stylesheets with overrides, but the admin theme is used. In particular this means that none of the front-end theme's twig templates are used for preview rendering. Is there any way to configure ckeditor 5 to use the front-end theme's template files? Otherwise this upgrade to ckeditor 5 is far off the ideal of WYSIWYG, actually it would be a step back from ckeditor 4.

Steps to reproduce

• Configure two text formats, one with ckeditor 4, one with ckeditor 5
• Customize some theme templates
• Switch between the two formats to see the difference in output, in particular that the ckeditor 5 uses the site's admin theme's templates for rendering the preview.

Proposed resolution

There should be an option to use the front-end theme's templates for rendering ckeditor 5 preview (WYSIWYG)