To hide specific app notifications on the lock screen:
- Long-press a specific app icon and drag up to app info, then choose the notification settings.
or, go to Settings > Notifications > select the specific app.
- Make your desired selection:
- Block all to turn off all notification of the app
- Treat as priority to let all notification be heard even when phone is set to priority mode
- Allow peeking to let heads-up notification show on current screen.