This tool lets you migrate your own posts from any subreddit to any Lemmy community you want, I made it because I couldn’t find anything else that did it the way I wanted to. I’m super happy how it turned out, I managed to get 9 years worth of posts over this way…
The GitHub link shows how to use it in case you want to!
Not only that, these presumably would all be old posts/comments being re-posted with current date/time. Maybe best to make sure the specific community or instance you’re sending this to accepts old Reddit content.
Interestingly this could be a use-case for Lemmy users having their own self named communities where they can dump old post/comment data into if they wish. e.g. for you it would be https://sopuli.xyz/c/MentalEdge (if it had existed).
It shows a top part in the post with original date and a perma link to said post like here: https://lemmy.emerald.show/post/764
