This is awesome.
However, are there limitations? I can’t seem to get rivers to show up as geolines. Roads work fine. Is that a limitation?
Topic on Talk:Map improvements 2018
It's hard to say without a wikidata id so I can look at what you're trying to display, but my guess is that the wikidata tag is on the OSM relation, not the ways. OSM type=waterway relations are not imported into the default osm2pgsql database. This should change when we roll out the style improvements, which include a database schema change.
The wikidata ID is Q1137387. Yes, it’s a type=waterway relation.
Are you rolling out the style improvements?
The OSM object is https://www.openstreetmap.org/relation/4638229, which will not be in a standard osm2pgsql database.
The development on style stuff is done, we just need to get it into production.