it works, if you shout something with your checkin or add an image (which you didn’t do here). the location is passed in the field ”location“ (just as quill and ownyourgram do it), the place name as ”place_name“ and the venue url as ”place_url“. knowns’ micropub endpoint seems to ignore those fields, but as you see, it got the syndication url (”syndication“) and the categories.
this is what gets sent: