How do I evaluate/test a .netstandard library

What's the best way of adhoc testing/coding When using .netstandard and/or .netcore?

I'm used to creating adhoc windows forms to test functionality in class libraries prior to integrating them into our code base. This approach enables me to single step the code, see what return values are, and most importantly dump output to a text box or grid. It's a useful way of digging into functionality. I also use this approach to create mini-apps for my own use, so I can just click the button, process some information and move on.

I'm now using a new library that targets .netstandard 2.1, and I find that my WinForms Framework app can't target that. If I move to Winforms Core then I'm forced to use the VS 2019 16.5 preview, which is ok for me but will be a barrier for our whole dev team. So what do I do? Use WPF forms for ad hoc testing, again ok for me but a pain for everyone else. I could use NUnit and single step but then I lose the output windows.