not an rss feed user so won’t be able to help much, but maybe you could add the images to the end in the feed file sort of like you add the carousel?
I see you have the carousel images listed in a data file, any reason you don’t just list them in the front matter? seems less complex.
my guess as to why they are not showing in the first place I think you already figured out, the carousel is using a background image css to show the file not an image tag.
Also one post I read said the images need the full absolut url which your img tag version doesn’t have, maybe that is the reason it doesn’t work?