Thank you for having a look at this.
I also thought about this. This is why I tried to keep a reference with

bpy.types.Object.current_draw_manager = draw_callback_handler

that allows to access the draw_callback_handler after the script terminated.
Even with the line above, the example script kept crashing. (However, I'm unsure if bpy.types.Object.current_draw_manager = draw_callback_handler achieves the intended effect.)

I've attached the latest version of the addon here:

I've investigated the crashing issue and found that they have been caused by bpy.types.SpaceView3D.draw_handler_remove(...).
I've added a corresponding ticket here: T86106

The problem that (large) point clouds can not be correctly represented with particle systems is discussed in this ticket: https://developer.blender.org/T81103

Thank you! This allows create a workaround (for previous Blender versions) when importing reconstructions with the photogrammetry addon.

Can you elaborate this a little bit?

Nice, thank you!

Added another ticket regarding the visibility of background images here: https://developer.blender.org/T85750

Strange, the system I mentioned above, i.e.

Operating system: Windows-10-10.0.18362-SP0 64 Bits
Graphics card: GeForce GTX TITAN X/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 451.48

has a dualboot installation (Windows + Linux). And for Linux it worked as expected.

Sorry for the delay ... - I had to meet several dealines in the past few weeks.

I was referring to tickets on the official Blender bug tracker.

Me too, sorry for the imprecise description.

Hi Robert, thank you for having a look.
Regarding bgl.GL_DEPTH_TEST I'll have another look. But (probably) it is a bug, since it works as expected under Linux, but not with Windows. The problem in this case is that the error did only appeared for large point clouds (and in a non-deterministic fashion).
Here an excerpt of an e-mail conversation I had with some reporting that bug:

In case this is not going to be fixed, is there currently any possibility to perform a joint rendering of elements of the GPU module and the 3D Viewport (with correct occlusion), which can be written to disk?

Hi Phillip,