Windows Service Template for Visual Studio 2017

Check the .NET desktop development option in the installer, then click Modify.

Just checked here. I see project "Windows Service (.NET Framework)" under the Windows Classic Desktop folder under Visual C#.

(Visual Basic has a similar entry.)

Only some templates are shown in parent folders, for more specialist templates you need to be more specific.

But also the search finds both.

NB I selected ".NET Desktop" workload on install, which I see you have not.