Each fediverse service is different. Matrix has it’s own webfinger configuration, as does diaspora, and mastodon. However, it looks like all ActivityPub services use the same webfinger configuration, which means that this method doesn’t work for donations trying to reference [email protected] for activitypub. I would presume that the first AP service you have listed in the response is going to be the account that each AP service will federate with.