You ought to be able to connect to Enterprise just fine. We use Make to generate reports from Survey123 forms, and we are connecting to our Enterprise Portal, not AGOL.
Well, perhaps Field Maps hasn't caught up with Survey123 in terms of the "out of the box" Make integration, but that doesn't mean it's impossible. If you're on a more recent version of Enterprise, you can create your own webhooks at the level of the service, then add a custom webhook to your Make scenario.
We're not at 11.0 yet but it's in our plan. Also, the only downside I could see to that is that an add/update/delete using that feature service would trigger the webhook. We would want to control which source is making the edit. For instance - only trigger a webhook if it's initiated from Field Maps. If it's edited using a web app, do not trigger the webhook.