Hook in wp.media to add a new tab

This is an issue coming up while creating a plugin. I want to add a tab to the wp.media.view.MediaFrame.Select modal or if a general approach helps:

In the customizer I want to hook in any modal that comes up using wp.media just to add an alert() for example.

This is almost it and I am already stuck in tracing what builds those modals and how to hook in.
What I see is:

• wp.media().frame.on('open', ...) can not be used as the frame only exists after clicking a button.
• Fallback may be to rewrite wp.media() but that doesn’t sound like a sane solution.

What I don’t want is:

• “Use media_upload_tabs or media_upload_tab_slug” because such PHP is not respected in the customizer.
• “Hook in every button and handle the click”
• “Look for frames via window.Timeout every second”
• Hacky solutions are welcome to find out what is possible but won’t help as THE solution.

Thanks in advance to all wp.media experts here! 🙂