Cannot specify specific OS version TFM in dotnet new

[dotMorten]

With dotnet new wpf I can specify either net6.0, net5.0, netcoreapp3.0 or netcoreapp3.1. The odd thing though is that if you specify net6.0 you actually get net6.0-windows.
However I wanted to specify a TFM a bit more specific than the default, so I used net6.0-windows10.0.19041.0, which is a valid TFM for the WPF template, however I'm met with the following:

Could the -f parameter be a little smarter and allow me to be more specific than the allowed TFMs, as long as it is a subset of them?

[baronfel]

This is very closely related to #4159.

The core issue that prevents a quick and easy solution is that the TFM is used not only in template generation (what we call 'instantiation') but also in template selection. Templates are grouped by a (GroupIdentity, TFM) tuple, because historically we've changed template contents based on the TFM. Adding the ability to specify the newer, platform-specific TFMs would require us to make changes to the template selection code to do a kind of 'template TFM supports user TFM' check. This is a fairly invasive change that will require a lot of testing.

We've seen a number of issues popping up related to TFMs and how they interact with template selection and instantiation that lead to a poor user experience. Our current plan is to solve them at the root by disentangling TFMs from the generation process with a new template generator geared for .NET projects specifically, instead of the very generic generator we're currently using. That work is tracked by this epic. In the interim, the workaround I can suggest is to generate the project and change the TFM after the project is generated.