actually, there is a quite elegant solution using grafana. Below a screenshot of some alerts I get on my phone through my telegram bot.
Home automation has two important aspects, GUI app of interacting with devices but also history, log database and charts dashboards, and for that task Grafana is the leader of both free and non free solutions probably. It offers all the tooling to set alerts depending on conditions, like minimum or even number of occurences of messages and so on.
You would need to have in addition influx as a database, I’m sure there are lots of youtube videos on how to achieve that with node red or other, I’m using my own python scripts, but this is a pretty standard solution. If anyone is interested and would like to use my python services to forward z2m messages to influx, I’ll provide help. I even added features to select mqtt subscriptions force types and discard unnecessary fields, also filter messages based on the last_seen value, which makes sense so that your entries do not get injected again on every subsciptions to mqtt for saved topics.