Not an RSS solution, also relies on US-based third parties.
replyFrom TFM:
reply> You can find the RSS feed for your publication at https://your.substack.com/feed.
> Replace "your" with the name of your Substack publication.
> You can find the RSS feed for your publication at https://your.substack.com/feed.
> Replace "your" with the name of your Substack publication.