lisakaye on "[Theme: Goran] Sidebar not showing on posts index page"

We don't provide private support for our free themes but I definitely believe you and will see if I can help out here.

As you already have Jetpack's Widget Visibility module active but aren't seeing the "Visibility" button when navigating to your widget's settings, there may be a conflict with another plugin on your site. Try not only deactivating, but permanently removing any standalone plugins that perform similar tasks to the Widget Visibility module. If that doesn't work, try deactivating your other plugins one by one.

If that doesn't resolve the issue, a standalone plugin may be a simpler option for you. A search for "Widget Visibility" in the plugin repository comes up with a lot of options for you to browse through:

https://wordpress.org/plugins/search.php?q=widget+visibility

You could have an experiment with them and then post to the plugin's support forum with any questions.

If you'd like to continue troubleshooting the issue with Jetpack then let me know, and I'll see how I can help there too.

What php page would I need to modify to hardcode which widget should appear on the News page?

That would be Edin's index.php file, however, as Goran is already a child theme to Edin, I recommend the plugin approach.