QGeoBoundingBox has bugs with the united() function.

The united() function (and the | and |= operators) misbehave when operating on two non-overlapping bounding boxes which are near to the date line but not crossing it.

The resulting bounding box should be the narrowest bounding box that contain the two, whereas it appears that uniting non-overlapping bounding boxes will never result in a bounding box that crosses the dateline, even if that is the documented behaviour.