Hi, just clarifying what I mentioned:
If I understand it correctly, the Jetpack Widget Visibility (https://jetpack.com/support/widget-visibility/) only displays the recent published articles. Is that correct?
Jetpack Widget Visibility controls whether or not any widget displays on a given page, even if that widget is just a HTML Hello World. You could have a widget with a cat image, and use visibility to only show that on posts or forum threads tagged “cat” for example.
You can test it by adding a widget to your forum page, then changing the visibility > taxonomy to only display under certain tags.
Developing the entire set of conditions or modifying your forums’ theme to include widgets would indeed be outside our ability to support you, but we can definitely explain our products features as needed. Hoping that helps!