Bokeh is an option in the frontend-viz space that puts out pretty solid SVG for statically-rendered charts, while also having the option of more Tableau-like interactive functionality with input fields, dynamic filters, etc. Might be a decent option for you?

Their interactive "embedded-mode" avoids iframes too... but it's built with web components, so you wind up in shadow-DOM hell if you want to do anything dynamic on the view's contents.

That's probably not trivial, but it seems plausible. The beauty of open source is that you can help contribute this if you're fired up about it!