Disable sound when a specific App shows a notification Is there a way I can allow notifications yet turn off notification sounds for one particular App? I want the notification sound to be off even if my phone is not on vibrate or silent mode. 

I am using a One Plus 5T running Android 9.0.8
I assume you mean OxygenOS 9.0.8, based on Android 9 Pie.

To do this, you can go to Settings > Apps and Notifications > See all apps

Scroll down the list to find your app and select it from the list.

Tap Notifications.

Choose which notification channel you would like to mute notifications from.

Tap Behavior and select your desired behavior.