I don’t watch a fantastic amount of S4C programmes to be honest (being more of a Radio Cymru person), but I’ve enjoyed the short series of programmes called “Dylan ar Daith”.
Dylan Iorwerth follows the footsteps of various 19th century Welsh travellers to various parts of the globe. I think there were 3 programmes in all, but one has expired. The 2 remaining ones should be around for a few weeks yet (as of 29/09/2017).
Subtitles available in Welsh and English. Sorry, UK only.
(Dylan also presents a discussion programme at 6pm on Mondays on Radio Cymru:
On a variety of topics: Welsh, national, and international).