Xamarin Android - Sqlclient is not supported on this platform

Question

Hi,
I'm developing a XF cross app.
I'm using some projects that are part of our company base's frameworks that run also in some our web application on .net standard 2.0.

Inside these frameworks there are some function that done the queries on a MSSQL DB and use the SqlCommand.

If I compile the frameworks's DLL and use them in my XF application all works fine, but if I add the project's framework to the XF solution an error is trigger only on the Android project when the app try to perform the first query.

As I told, if I use only the compiled DLL all works fine.
For the iOS project works also with the project's frameworks.

The frameworks use the NuGet package System.Data.SqlClient, and the mobile app Microsoft.Data.Sqlite.Core.

We have tried both with Microsoft.Data.SqlClient and with System.Data.SqlClient.
For System.Data I have tried with multiple versions:

-4.8

-4.7

-4.6

-4.5

We need to have the project's frameworks inside the XF solution to debug them.

How can we solve this?