I'm the head mod of a pretty big subreddit, /r/3Dprinting, with 7 million views a month and 1.8 million subscribers. At the beginning of this I set up a lemmy instance at https://rhombik.com and linked to it from that subreddit. From the roughly 150k uniques per day we had on /r/3Dprinting zero of them have tried the lemmy instance.
So make of that what you will.