Is MS SQL Server 2017 Supported as Data source?

It is not officially supported as of now for 18.2 or earlier releases according to the info on this page: docs.appian.com/.../System_Requirements.html
Support should be added in the next 2-3 releases, as it should be tested by Appian engineers first and any required tweaking should be done for Appian product.
Still you can try to use it for some non-critical environment and test your applications there.

It is not officially supported as of now for 18.2 or earlier releases according to the info on this page: docs.appian.com/.../System_Requirements.html
Support should be added in the next 2-3 releases, as it should be tested by Appian engineers first and any required tweaking should be done for Appian product.
Still you can try to use it for some non-critical environment and test your applications there.