How to send notification to specific phone

I have built an app using Thunkable and Xano and need to know how to send a notification to a specific phone whether or not my app is currently running.

Looking at OneSignal it does not recommend using an API to send push notifications to mobile devices and instead steers people towards an SDK. As a no-code developer, I can't use the SDK.

The scenario is that when a record is written to a specific table in the database, a push notification needs to be send to the phone associated with the record.

Does anyone have any recommendations on how to do this?