The developer for the Easy Real Estate plugin that generates the pages where the widgets show, said they are not related to the plugin
Here’s a piece of evidence that says otherwise: The exact template that outputs that page’s content. It came from the plugin and it calls for a sidebar.
If there’s a way to copy that template into a child theme then you may be able to remove that sidebar line and make it work. But this is something the plugin author would know or he may have already documented this somewhere.
If the author designed the plugin to work with specific themes then you may have to find another theme that’s intended for that particular plugin.