lemmy has multiple implementations already
No it doesn’t? There is only one Lemmy implementation. There are some similar alternatives like PieFed and Mbin but those are separate implementations and are not in any way related to Lemmy, aside from using the same ActivityPub extensions.
There is really no such thing as a “platform type” - it’s all ActvityPub under the hood.
You’re talking about Sublinks and it has yet to reach a usable state. It doesn’t seem like development is going particularly fast.