I had figured out how to make this work using https://de.www.ads-software.com/plugins/sb-rss-feed-plus/ for generate the feed.
In the configuration of the feed-plus the plugin generate a hash the call “SPECIAL URL” so the url will be something like https://yoursite.com/feed/?fsk=1234 use this url with hash instead of the /feed/ only and the images will work.
Good luck
