There are import scripts - the problem is that Reddit has disabled the Pushshift API end of March, which makes data exporting significantly harder. There are some archives from before that available as torrent, and there has been effort from r/datahoarders to archive and submit it to archive.org before the shutdown.

I’ve been looking into that for our sub, and concluded it’s currently not sensible - so in case we decide to reopen restricted for archive access I created a bot that re-posts Lemmy postings into the locked subreddit for discoverability, and adds a comment to drive users out for commenting.