Do real-world ActivityPub implementations support type property that's an array? Like in this figure from the spec: https://www.w3.org/TR/activitystreams-core/#fig-an-object-that-is-both-a-place-and-a-gr-location

I glanced at #Mastodon source, they are using a library for json-ld, so should be able to deserialize at least, but I'm not sure if they don't do obj["type"] == "Note" internally.

#Pleroma seem to do just that, so if type is an array, Pleroma will just fail.

Not sure about other implementations (#PeerTube, #Misskey, #Pixelfed etc.).

Put another way: do Fediverse servers fully implement JSON-LD, or do they treat documents as fancy JSON?