I want to stop Apple News notifications on my Mac

This must be Unique to your computer

Start now and open an Apple Support Ticket as they are PAID  Apple Employees to deal will these types of issues .

Other location Call Centres 

 Contact Apple for support and service

There are some ( not all ) who come to these Forums seeking Technical Answers to Technical Apple Issues

Then there are some who come seeking their moment of fame 

Unlikely: are you possibly getting notification summaries from AI?

Summarize notifications and reduce interruptions with Apple Intelligence on Mac - Apple Support

Otherwise, contact Apple. With no News app installed and no notifications enabled, there’s something odd happening here.

The Apple News Application is Built into the Operating System

At least, it is installed on 4 different Apple Computers I use each will macOS 15.1 Sequoia

Check again using Finder >> Go >> Applications

Check again using Finder >> Go >> Applications

Go to System Settings > Notifications. Then find the News app in the list on the right. Select it and toggle off

"Allow Notifications".

Another way: Open the news app. Then select help in top menu and then type in notifications. A list appears. Uncheck all of the notification links for the various news medias.