the +Sub in url still work:

https://www.reddit.com/r/AdviceAnimals+BlackPeopleTwitter+DIY+Documentaries+EarthPorn+Futurology+GetMotivated+askscience+aww+bestof+dankmemes+dataisbeautiful+europe+explainlikeimfive+facepalm+funny+gaming+gifs+history/rising/

The limit seems to be at 20 subs added, or dependant of the size of sub (the list above are some of the most followed sub); you can have more if they are less followed it seems like this:

https://www.reddit.com/r/AfterTheCredits+AndroidGaming+Anthropology+Anticonsumption+ArtFundamentals+Berserk+BigBrother+Blogging+BollywoodRealism+Design+FanTheories+FlashGames+Foodforthought+Games+HailCorporate+IWantToLearn+IndieGame+IndieGaming+JudgeJudy+KeepWriting+LifeProTips+MetaWebGames+MuseumOfReddit+OPDelivers+Piracy+PropagandaPosters+SRSBusiness+ShittyFanTheories+Simulate+Stingray+TrueFilm+TrueReddit+WebGames+WorkOnline+YouShouldPlay+antigoogle+askscience+browsermmo+cerebral+claymore+controllablewebcams+dating_advice+debunked+europe+exjew+femalefashionadvice+freebies+freegames+freelanceWriters+gameai+gamedev+getdisciplined+idlechampions+innergame+learndesign+lifehacks+longtext+loseit+ludology+malefashionadvice+nathanforyou+onlinegames+opensourcegames+patientgamers+playmygame+plotholes+postnationalist+privacy+proceduralgeneration+programming+relationships+roguelikedev+roguelikes+rpgWebGame+rpg_gamers+rupaulsdragrace+scifiwriting+selfpublish+simpleliving+skeptic+socialskills+survivor+tbs+thatsneat+tipofmytongue+truePrettyGUglyFace+truegaming+undelete+videogaming4free+wesnoth+windows8+write+writing+wrpg+wtfstockphotos/