Hello @bmaas1
Thank you for contacting the Instructure Community. The short answer is - not really. Ideally, you could make the discussion graded and worth 0 points so that you can use the speedgrader and quickly see which students have submitted and which haven't. Besides that, you'd need to manually look through the discussion and view which students have contributed. Sometimes, we can run API calls to get lists for things like this but it doesn't look like the call exists for your specific request:
https://canvas.instructure.com/doc/api/assignments.html
Perhaps other users have found alternatives but those are likely your options without running other reports - but even then - most of those require them to be "assignments" to compile a list or csv of which users didn't contribute.