I’m trying to figure out how to get hachyderm.io posts to show up on my “Subscribed” feed in Lemmy, but i think I’m missing something
It’s not currently possible, but it’s possible for a Mastodon user to subscribe a Lemmy community.
AFAIK, it’s not possible to subscribe to a Mastodon user nor a Mastodon server from Lemmy; you’d need a Mastodon/Pleroma/etc. account.
Lemmy is for link aggregation and Mastodon is for microblogging. The difference being that Lemmy is for having interesting, constructive conversations with people of similar interests and Mastodon is for pointless arguments with strangers.