Adding ads into feeds works, just make them an entry in the feed. I have also seen embedded images with ads. Issue is that Google Ads and such don't offer this

Adding ads into feeds works, just make them an entry in the feed. I have also seen embedded images with ads. Issue is that Google Ads and such don't offer this and you don't get the "typical" ad networks. If RSS were more popular there wouldn't be a problem to build the required tooling. Even when feed readers don't send cookies etc. while fetching you can do a permanent redirect to a feed with an unique ID in the URL and most feed readers will store that URL, thus you can do tracking (incl. personalizing URLs in the feed) and all that. What saves reader privacy currently is the small user base.