I already encountered this a few times while searching for something specific. Even though the protests are understandable it makes it so much harder to find information.
But for real. You can use something like a webscraper that crawls reddit via the normal web interface and create a bot account on lemmy. Then just download the reddit posts and upload them to lemmy.
I would not recommend this as lemmy.ml is currently almost at capacity and uploading tons of reddit posts does not help.