I'm working with a client on doing some "secure" iFrame stuff using an HTML5 video player in an iFrame. This is SharePoint 2013 on-prem but hosted in the cloud by Microsoft. YouTube embeds and the like work great -- when I put in the iFrame, it stays a Snippet and embeds the content perfectly on desktop and the mobile view.
However, when I try to iFrame in a page from the same SharePoint site as the destination page, it forces a Web Part and thus won't show up in the mobile view. I've added the domain to HTML Field Security, which seems to work when hosting my iFrame page on other domains, but not when it's on the same domain.
Is this a known limitation that I'm not aware of? How can I iFrame in an HTML page hosted on the same domain into a SharePoint page without losing mobile compatibility?
Any help is more than appreciated!