Thank you @Ivanidzo4ka .. if I agree with everything you say. To refine and make a best test, we have also spoken about having an abstract environment class capable of outputting to a user's preferred logging framework, it might be nice indeed if this thing followed that example -- if it cannot that might itself be a test that the leve of abtraction imagined is insufficient.

Can I take a shot at this? What would I have to do? (If it's still an open issue)

Feel free to.
Where is thing you need to be aware of. XUnit IOutputHelper (or whats the interface for outputing) doesn't support Write, it support only WriteLIne (which starts new line) and our channels can send only write messages.
Also I think we have quite a lot of tests where we capture output from console, and compare it with baseline. I would like to switch it to XUnit Environment, but it need to write to console as well.

In terms of what you need to do, you need to implement class based on IHostEnviroment interface inside TestFramework project, which would consume channel messages and propagate them to IOutputHelper.
As example I would suggest you to look on ConsoleEnvironment class and it's ConsoleWriter object