@David Griffith Thank you for your query!!!
As per this post :
Unfortunately, the port for ACI to exposed to the Internet should be a unique one, it means the port only can appear one time. You won't be able to use Port 3478 for both UDP and TCP since it is currently not supported on ACI.
Same has been shared as feedback on our forum as well here. I will suggest you to go ahead and upvote the feature request since our Product Group actively look into those forums and the post with good number of upvotes are taken into consideration and worked upon.
Hope it helps!!!
Please "Accept as Answer" if it helped so it can help others in community looking for help on similar topics.