I've released version 2.0.0 of my RSS to ActivityPub converter! This now provides functionality I'd hacked in to https://rss.friend.camp - it requires OAuth 2.0 authorization for someone to create a new AP account for an RSS feed.
I used to run this service "in the open" but was overwhelmed by spammers. Now the admin of a Mastodon (or Pleroma or any federated server that is an OAuth 2 provider) can provide this converter as a service solely to members of their instance.
https://github.com/dariusk/rss-to-activitypub/releases/tag/v2.0.0