mqttwarn is a highly configurable MQTT message router, where the routing
targets are notification plugins, primarily written in Python.

mqttwarn subscribes to any number of MQTT topics and publishes received
payloads to one or more notification services after optionally applying
sophisticated transformations.

It comes with over 70 notification handler plugins covering a wide range
of notification services, and has an adapter for the Apprise notification
library, covering another set of 80+ notification services.

Repository: https://github.com/jpmens/mqttwarn
Documentation: https://mqttwarn.readthedocs.io/