Good point.
In the meantime, you can create an empty Notify Group. Then create an automation that triggers on that notification.
notify:
- platform: group
name: xxx
services: []
automation:
- trigger:
platform: event
event_type: call_service
event_data:
domain: notify
service: xxx
action:
- service: ...
In the alert use xxx as the notifier. Kind of a hack, but it should work.