When looking for this location, I found that the town of Neapoli itself was too low against the mountains compared to some of the scenes of the house. However, after finding the right elevation in Street View, I could work out the general area that the crew would’ve filmed from.
It was clear that the general area was Vryses. Scanning the streets, I couldn’t see anything similar using Google Maps around the town so I decided to check the more famous landmarks – it was evident that the series was also used as a tourism vehicle so it did use quite a few famous places (Gorges, Churches and so on).
On checking photos of the Monastery of Kremasta, it looks like the archway we see every time in the series is still there.
Notice the same details in the Tripadvisor photo below. The style of archway, the telegraph pole and the door to the right are all still there.
In other episodes, we see another view from the other side of the archway door. We frequently see Matheos climbing the stairs and turning to the right behind the building on the upper level.
Who Pays The Ferryman? Locations Page 