I don’t use mobile, but I just tried it on a “smart” phone, and it’s broken for me too. Exactly like you wrote, I see a drop-down menu which lets me select Social or Meta, but doing so has no effect on which questions are shown. However I can hack around it by going to the URL field in the browser and adding /browse/social to the web address, i.e.: i.fluther.com/browse/social or i.fluther.com/browse/meta will show the other sections.