I am currently testing OH2 and facing a problem with the set point widget inside the classic ui and iOS app. It looks a bit like the problem is caused by the auto detected homematic devices. (I am currently using the new Homematic Binding from https://github.com/gerrieg/openhab2).
Does anyone tried the iOS app with OH2 and auto discovered things?
Note that Things (and therefore auto-discovery) have nothing to do with the UIs, which merely operate on items.
So any sitemap that contains setpoint widgets and works on openHAB 1 should also work as is in openHAB 2 (with all UIs).
Your problem might be that you are using the dynamically constructed sitemap (i.e. _default). These cannot determine special widget types such as setpoints and thus will rather use plain text widgets or similar. But this is fully expected behavior for now. Simply design your own custom sitemap and all will work as you desire.