I stored data in GeoJSON format on Commons: Data:Lychener Pinnenpfad.map
On Wikivoyage the template Mapframe works perfectly with Markers and vCards: Lychener_Pinnenpfad
Since this can't be done on Wikipedia, I put an image on the Lychen page linking to Wikivoyage: Lychen#Tourismus
As far as I understand, Wikipedia recommends the Template:Mapbox for this purpose: Template:Mapbox
I didn't succeed getting my data into this template.