How to connect to SharePoint 2010

[Maksim2030]

I have internet site URL, user name and password for SharePoint 2010 on-premise.
I wont to connect to sharePoint 2010.
var authenticationManager = new PnP.Framework.AuthenticationManager(); var clientContext = authenticationManager.GetOnPremisesContext(url, userName, password.ToSecureString());

I see error: Cannot access internal method 'GetOnPremisesContext' here.
How I can connect to SharePoint 2010 with PnP.Framework?

[Maksim2030]

net45 project
I'm using ClientContext from assembly: Microsoft.SharePoint.Client, Version=16.1.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c
Assembly location: ...\.nuget\packages\microsoft.sharepointonline.csom\16.1.20122.12000\lib\net45\Microsoft.SharePoint.Client.dll

It works for net45 project
ClientContext context = new ClientContext(onpremSiteUrl);
context.Credentials = new NetworkCredential(onpremUserName, onpremUserPassword);;
context.AuthenticationMode = ClientAuthenticationMode.Default;
context.Load(context.Web);
context.ExecuteQuery();

netstandard2.0 project
I'm using ClientContext from assembly: Microsoft.SharePoint.Client, Version=16.1.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c
Assembly location: ...\.nuget\packages\microsoft.sharepointonline.csom\16.1.21312.12000\lib\netstandard2.0\Microsoft.SharePoint.Client.dll

It does not work for netstandard2.0 project
The remote server returned an error: (401) Unauthorized.

ClientContext context = new ClientContext(onpremSiteUrl);
context.Credentials = new NetworkCredential(onpremUserName, onpremUserPassword);;
//context.AuthenticationMode = ClientAuthenticationMode.Default; // missing in ClientRuntimeContext
context.Load(context.Web);
context.ExecuteQuery();