Having established that the laser beam comes out of the lens perpendicular to the honeycomb platform surface, this seemed peculiar:
The mirror 3 + lens tube has a distinct tilt when seen from the +X direction (the right side of the machine, so it’s in the YZ plane, I suppose).
This is not matched when seen from the -Y direction (front):
The tilt does not seen to correct for a misalignment in the X axis rail or the brackets attaching the head to the linear bearing.
The beam seems properly centered on the lens and nozzle, so I’m loath to twiddle the alignment just to see what happens. One of these days, for sure, that must happen …