Quick Update: Microsoft introduced new output option of Azure Stream Analytics job to Azure PostgreSQL (Preview):
This new output option to Azure PostgreSQL allows customer to write output streaming/analytics data into relational database.
With this new output, Azure Stream Analytics jobs write to Azure PostgreSQL Single Server, Flexible Server (Preview) and Hyperscale (Citus), supporting high throughput insert of streaming data to existing table.
Azure SQL database and synapse analytics were already there as output option for streaming job. Streaming input option remain same: Blob Storage/ADLS GEN2, IoT Hub & Event Hub.