A. Create a relationship class between the features and the table
B. Create an in-memory relate in the Contents pane
C. Copy the data to a file geodatabase, compress to zipfile, and publish as an item
D. Create a temporary join in the Contents pane
Explanation:
Reference: https://community.esri.com/thread/198458-publish-hosted-feature-service-with-related-tableswont-work-with-arcgis-pro-20