Extra space around editor canvas and extra scrollbars in non iframe editor

[yankiara]

OK new update, I could fix the editor with this option checked:

So, what are those certain condition mentioned here that could prevent Gutenberg to launch the iframe mode? And can we do something about it ?

I guess this is related:

WP iFrame editor for posts & pages

Yes, it appears this is another case of the grasp exceeding the reach… we were looking forward to this in WP 6.2 for a smoother more consistent editing experience for our clients. Currently the 2 restrictions that make a difference are not being able to use metaboxes and requiring the Gutenberg plugin. It seems that will limit it from being used in a lot of cases in the short term. Hopefully things will become clearer in time.