Or, just use a proper JSON-LD processor altogether. Of course, there would be a performance penalty. The #ActivityPub spec explicitly allows as:Public or bare Public for public addressing in to/cc, etc., but surprisingly many implementations don't handle this. All of this would actually be solved by using a JSON-LD processor.
w3.org
ActivityPub
The ActivityPub protocol is a decentralized social networking protocol based upon the [ActivityStreams] 2.0 data format. It provides a client to server API for creating, updating and deleting content, as well as a federated server to server API for delivering notifications and content.
