@boby_biq you go to a feed (channel? sub?) in Lemmy, and copy the sub's address into the search of mastodon. (replace the ! with @)
in this example, take "!nathanwpyle@lemmy.world" and paste it in mastodon as @nathanwpyle
Does it just show you new posts sent to your actor inbox? When I look up lemmy communities on mastodon or calckey i see the profile but no post history