SharePoint Teams Notifications

The news publisher cannot disable these new post notifications while publishing it. However, individual users can turn them off notifications at their own level. SharePoint / Global Admins can also disable all notifications from the admin center, but that will turn off other notifications as well. At this time, there’s no option to disable only the notifications for new posts.

This isn’t something you can disable centrally or per news post. Microsoft currently does not provide a tenant-level or SharePoint setting to prevent Teams notifications when publishing a SharePoint news article. When news appears in Microsoft Teams, this happens via Viva Connections, and the notification behavior is intentionally controlled at the user level, not by the publisher.
https://learn.microsoft.com/en-us/troubleshoot/microsoftteams/teams-administration/disable-sharepoint-news-notifications