See https://ro.wikipedia.org/w/index.php?title=Utilizator:Strainu/2&oldid=10737958 According to https://www.mediawiki.org/wiki/Help:Extension:Kartographer#.3Cmaplink.3E , "The <maplink> tag may contain the same geojson as <mapframe>.", presumably with the same effect.

The geojson is shown correctly on http://geojson.io , but not on the pop-up map (nothing is shown there). I did notice that at some point I was able to click on the coordinates and was taken to https://ro.wikipedia.org/wiki/Special:Map/16/44.419701/26.139964 , where the coordinates are displayed. I was not able to reproduce the behavior, but I guess it has something to do with JS not getting fully loaded before I clicked the link.