I'm challenging myself for a few hours now attempting to remove the
s4-ribbonrow from a modal dialog window (as marked in my screenshot). I found several solutions on the web, which all require SharePoint Designer 2013 or any access to the SP master page. The problem is, that I am only responsible for some page which is far under the top level site and therefore I only could switch it off with Script Editor WebPart.
I've tried to code it like:
But unfortunately it doesn’t change anything and I still can see the ribbon.