a fountain’s coordinates/node id by tag wikidata=Q…

Hi

This is the correct place for newbie questions.

This will return what you want:

node[amenity=fountain][wikidata=Q83630092];
out center;

https://overpass-turbo.eu/s/Q62

If you don't know if the entity was mapped as a single point, swap node for nwr (Node, Way, Relation),

If you want to search for all in area of visible screen:

[bbox:{{bbox}}];
nwr[amenity=fountain][wikidata];
out geom;

https://overpass-turbo.eu/s/Q64

You should be able to work out how to filter for drinking_water from these examples.

If you want to output as a CSV list, add [out:csv(::id, "name", "wikidata"; false; ",")] as line one.

To tie in with your other posted question - to find entities which don't have name (or wikipedia) tags add an exclamation mark:

[bbox:{{bbox}}];
nwr[amenity=fountain][wikidata][!name];
out geom;