How can we make Non Working server RSA key length to 2048?
Use a company certificate that has the key length you'd like.
If you're relying on the self generated certificates created by SQL Server as a nicety, then you'll instead want to use your own as there is no way to change that, it's hard coded.
For completeness, other items associated with this issue.
Connection string keywords for Microsoft-supplied SQL Server drivers vary by API. The documentation is included with the API-specific driver documentation.
Below are links to the official Microsoft documentation connection string keyword pages for some commonly used drivers. I did not include older and legacy drivers as those should not generally be used for ...