Although it’s possible to follow Lemmy’s communities in Mastodon, I would not suggest it as the experience is not the same. That’s my reason to have separate accounts.
If you only want to be “notified” of new posts in a given community, I think you can subscribe to some sort of RSS feed. In Calckey (now Firefish), you can add timelines that will show specific RSSs.
If such setting is implemented, please don’t limit it to a single language. Many people knows multiple ones while still wanting to filter out all the other languages they are not familiar with.