If you make everyone watch that category, they’ll get a notification when something is posted on that category.
Seems like an edge case. A plugin wouldn’t be hard to do.
Looks like automation has only Post created/edited, so you could post those updates to a (perhaps unlisted or unreadable) topic instead of, or in addition to the category.
A feature request for am automation trigger of new topic in category seems like it could be a reasonable request.