I’d suggest leaving out the redirect. Just have it so that when the button is clicked, its content is updated to display a loading spinner and text similar to “publishing topic…” Once the topic is published, change the button’s text to something like “visit topic to start the discussion.”
It sounds like Angus is considering adding a “publish to Discourse” shortcode and block to the plugin’s next release: An idea for more economical comments? - #15 by angus. It’s likely that could meet your requirements.