Any idea how I can make a script inside the turbo frame loaded in the modal initialize when the frame is loaded? It works fine when I have the frame loaded inline with other divs on the page (UI) but fails to initialize when the frame is loaded in the modal.

Just adding my ¢2 but the appeal of other editors over ActionText is that they add semantically correct HTML code (paragraphs instead of div+br, etc.) and, depending on the editor, allow one to define and drop/drag in custom content elements. There are kind of workarounds for ActionText but they tend to be too much hassle in most cases. My vote would be for an example using Redactor but, bottom line, would be an episode that shows how to use a different editor and custom content blocks while retaining the automatic content (images, etc.) uploads via drag and drop.