I do not think so there is a built in way you can fetch incoming WhatsApp media without a webhook/trigger, and as the whatsapp cloud only works with webhooks so you must use the webhook trigger OR there is a way you can use Custom HTTP request with webhook to receive and then download whatsapp media, you can consider this:
Also when using custom HTTP node make sure to always stay within the limts:
in practice, n8n has absolutely no way to know a file even exists without that initial trigger. you must use a webhook (like the whatsapp trigger node) to catch the incoming message and get the unique media id. once the webhook gives you that id, you just drop it into a standard whatsapp node set to media → download to actually grab the file.
The others have it right, you can’t really skip the webhook step here. WhatsApp’s API is designed around webhooks so there’s no way to poll or list incoming media, you only get the media_id when Meta sends you that webhook notification about a new message. Once you have the id though you can use the WhatsApp node’s Download Media operation to grab the file, or if that gives you trouble (it sometimes returns a URL instead of the binary) you can hit the Graph API directly with an HTTP Request node using your WhatsApp credentials. Is there a reason you’re trying to avoid the webhook? If it’s a hosting issue or something there might be a workaround.