It's not currently possible, but it's possible for a Mastodon user to subscribe a Lemmy community.
Lemmy.ca's Main Community
Welcome to lemmy.ca's c/main!
Since everyone on lemmy.ca gets subscribed here, this is the place to chat about the goings on at lemmy.ca, support-type items, suggestions, etc.
Announcements can be found at https://lemmy.ca/c/meta
For support related to this instance, use https://lemmy.ca/c/lemmy_ca_support
How's that work when a mastodon account pulls lemmy feeds? Is everything a chat message, then? (caution: I am new, I may not Grok mastodon, so make no assumptions or leaps!)
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.