how can i catch all stripe webhook events that are not explicitly handled?

Stripe recommends only subscribing to events necessary for your business, so if you did discover subscribed events you aren’t handling a good option would be to unsubscribe from them.

If you want to do some processing for all events, it looks like dj-stripe has a handler_all option (code). You’d likely want to maintain some dictionary of explicit event types you handle and check if the received event is handled before logging your unhandled event.