nostr:npub1m299scpk0n8gqnjkmftjzr56mqa4zqlxkwha7p43c7y6zusw5deslhkhl9

>different profiles for different activity types

Do you mean different ActivityPub actors?

In Lemmy there could be a user and a group with the same username on the same server. To distinguish between two actors they use properties object:

https://lemmy.ml/.well-known/webfinger?resource=acct:activitypub@lemmy.ml