I too have a wp 5 related issue. It’s the description text field when creating an event. It’s WYSIWYG editor and now with the gutenberg added to wp, the text field is sort og still there, but there is no way to edit the text and the text is white… on white background… Slightly difficult to edit that way ??
Is there a way to either incorporate gutenberg in the text editor, or make the text field work again in another way?