Unable to answer "Is drinking water available here? If so, what is its source?" – west point on the eno (Drinking Water) – https://osm.org/node/4573711703 via StreetComplete 59.3:

This is actually a restroom not a water source.
There's a covered picnic table area on top

Attached photo(s):
https://westnordost.de/p/250546.jpg
https://westnordost.de/p/250547.jpg