making norns receive osc is not really the issue
i think the ‘difficulty’ is , how do you plan to generate the encoder and button events?
afaik, this is not exposed to lua, so you are going to have to do this by forking/extending matron.
if you have the relevant skills to understand the matron C code, its not too hard, but likely to be fiddly (if my experience with push2 is to go by) … the event generation is ‘easy’ , the main bit is wiring it (possibly via oracle?)
as for Arc, would have thought the arc support would eventually be added ‘natively’ rather than going via an OSC bridge, Id have thought that approach would be pretty simple.
(wether encoder events are the right thing to be throwing to lua from an Arc is another matter (given the current acceleration code etc)