WKGTK 2.6.4 (also noticed in previous versions) and MiniBrowser (also reproducible with Epiphany 3.14.1). Logged in in Flickr and going to the organizer. Try to set the location of a picture. Yahoo's map loads but dragging the map through clicking and zooming through the wheelchair or by double clicking doesn't work. This works when in https://maps.yahoo.com so it is a specific problem in the Flickr organizer.
Still reproducible with WKGTK 2.15.3 (also noticed in previous versions) and MiniBrowser (also reproducible with Epiphany 3.20.6).
Do you see anything in the web inspector? I wonder if it's another instance of a website ignoring mouse events when it detects that touch events are supported. Any chance the page uses jQuery?
I have similar problem with Apple Maps in DuckDuckGo.com results - I can zoom with mousewheel/touchpad scrolling, but I cannot drag the map anywhere. This is in Epiphany Nightly (flatpak, 3.35.90-12-gd41289ee1; webkit 2.27.4), but it also occured in older versions (minimum Ephy 3.28 and webkit 2.24). Works fine in Firefox btw. Should I open a new issue?