The venerable .NET Framework 2.0 up to version 3.5 are still very much in use today. Although not as modern and feature rich as the releases that followed, the old guard has proven itself. Software developers don't feel compelled to migrate their tried-and-tested code. Thus administrators end up needing this Framework even on their spanking new Windows 2019 servers.

The Windows Server Manager is the starting point for adding features. However going through the wizard in full automatic mode doesn't work as expected. And even though the solution will be staring at us, it can be easily missed.

This is the error the Add Roles and Features Wizard reports unless we do it right:
The request to add or remove features on the specified server failed. Installation of one or more roles, role services, or features failed. Error: 0x800F0950

Solution

1. Start from:
   Server Manager | Add Roles and Features Wizard

2. Move on through the Wizard steps up to the feature selection.

   

3. Select .Net Framework 3.5 Features and click Next. Note that .NET Framework 3.5 satisfies .Net 2.0 requirements as well.

4. We now get to the Confirm installation selections step

   

5. Note the warning at the top. It really gives us an important hint. If we ignore this and click Install the installation fails as shown at the beginning.

   Do you need to specify an alternate source path? One or more installation selections are missing source files on the destination server. The server will try to get missing source files from Windows Update, or from a location that is specified by Group Policy. You can also click the "Specify an alternate source path" link on this page to provide a valid location for the source files.

6. Insert the Windows 2019 installation media.

7. Click Specify an alternate source path

   

8. Specify the path that follows and click OK. You will find the necessary installation here:
   X:\sources\sxs

   X: is my Window 2019 media drive.

9. We are now back at the main Wizard Confirm installation selections step. Click Install now.

10. Installation should now succeed

    

Final Tips

Looks like Windows 2019 is having a hard time fetching the older .Net Framework. We will need to keep that installation media handy to complete this task. This can be a bit of a nuisance but if you overcome this hurdle the old Framework will soldier on just like it has been doing for so many years.