I’m not sure if this is new, but when I clicked on the /r/pics protest post link from the frontpage here, I was redirected to this: https://old.reddit.com/premium
I’m not sure if this is well-known or not that they’re pushing it now, but it’s the first time I’ve seen it, especially on old.reddit.
I just use Firefox with the standard ad blocking extensions and I’ve never seen an ad on new Reddit.