Since wpForo doesn't seem to work with other plugins, perhaps dropping it in favor of vanilla WordPress is the best way forward.
It's also about whether the wpForo team provides users the support they need to integrate plugins. I first posted this issue 9 days ago and have yet to receive a response that even points me in the right direction. Forminator support, in contrast, has identified the likely issue and provided sample code that would help if wpForo reciprocated.
Navigate to Dashboard > wpForo > Settings > Posting & Editor Settings, insert the below code to Allow extra HTML tags field:
, link(rel href media id), style(id)
Make sure that "Enable WordPress Shortcodes in Post Content" option is enabled
Then Navigate to wpForo > Settings > Colors & Styles and insert the CSS code that Patrick – WPMU DEV Support has provided.