nostr:npub17dltk44gs52vp3yqt2sexqp8ftzxful0pk5tluz0kgtcs2xsjdtq5cdj38 Lemmy accepts Follow, Like and Create activities, so follows, likes and replies from Mastodon should work.

Among activities Lemmy sends, Mastodon should be able to process group announcements and replies.

>And how do I post to Lemmy from mastodon with decent format?(if possible)

The first line gets transformed into a title.