Hi @beasteers and @melori.arellano
I use the webhook contact point in Grafana alerting to send the notification to Node-RED, which receives the webhook and then sends a sound signal or audio message over a PA system. If listmonk (or a similar service) can receive a webhook and then send out mass emails to the subscribers of that service, then I think this can all be done in much the same way.
Here is the thread where I detailed the webhook-to-audio alert solution using Node-RED.