Is OSC / TUIO supported in UE4?

No and Yes. No by default engine code, Yes if you implement support for reacTIVision to the engine via C++. Best to do that is by making plugin as then you can easily redistribute support for that to others:)

https://docs.unrealengine.com/latest/FRA/Programming/Plugins/index.html

If you what more help with this i think best would be ask people working on Kinect support for UE4 since those technologies are kind of similar