If we look to podcasts as a model — 490K new episodes in the last 90 days, delivered to users and to aggregators alike via "not dead yet" RSS — ads are placed inline with the content. There is no RSS-related "pact" that precludes the relationships you mentioned.
Related analyst estimate: "US podcast ad spending will surpass $2 billion in 2023 and will account for nearly one-third of digital audio services ad spending." https://www.insiderintelligence.com/content/us-podcast-adver...