Nice catch! This is because the “Continue to the app” link makes a custom URL request that starts with org.jitsi.meet://. I have whitelisted that custom query scheme in DiscourseHub, which should fix the issue there on the next app release. (I don’t think there is a fix for this in Chrome, alas.)
I have added a randomly-generated option, users just need to leave the ID field empty, and an ID will be generated. I also added some copy to explain this:
Note that the ID won’t have words, it will be a random mix of letters and numbers.