I was also facing the same issue while writing to a sql server. Was able to resolve it by updating the format to "jdbc" instead of "com.micorsoft.sqlserver.jdbc.spark".

df.write.format("jdbc") works on DBR 13.3 LTS using the connector: com.microsoft.azure:spark-mssql-connector_2.12:1.2.0

Source where the solution is mentioned: https://github.com/microsoft/sql-spark-connector/issues/191