Unfortunately I don’t think so, but I’d love to be wrong on that. I will look into whether we can improve the error message here so it gives you instructions on how to add the bot to the channel.
good point. We can certainly update the default to remove the word ‘Discourse’. But in the meantime, you should be able to search for “Continue on Discourse” in the admin panel and change it to whatever you like: Customize all text in Discourse
Edit: default button text is now Continue on Forum