Oh, that's interesting. I was hoping a scraper would emerge. Stealth's scraper (currently) doesn't seem to actually display content that is marked nsfw. Maybe they haven't yet figured out how to detect/accept the confirm 18+ barrier on old.reddit.com.
I had no problems going to a NSFW sub. If you go to Settings > Reddit Source and try either Reddit or Reddit (Web Scrapper), maybe one or the other will work?