I have reviewed the configuration and do not see any issues with authentication to ServiceNow using the U2M approach (OAuth application with an Integration User).

However, I would like to understand which user context is used when the data fetch occurs during pipeline execution.

Based on my observations, the ServiceNow integration user is not being used during pipeline execution. As a result, no data is returned.
When ServiceNow admin privileges are assigned to the AD user who logged into the Databricks workspace, the ServiceNow table data becomes visible.