The LG G6 doesn't perform well in low-light. I've been inspecting many camera sample taken at night or indoors and you can clearly see that the small 1.12-micron pixels of the Sony IMX258 sensor directly impact the low-light performance. This becomes even more severe in the second wide-angle camera that uses the same sensor but with an even slower f/2.4 aperture, compared to f/1.8 on the primary one. There is a dual-LED flash on the G6, but it doesn't help for most situations, in which you want the entire scene to be have optimal exposure, not just of a subject close to the camera. You can see that even a super bright f/1.8 aperture can't fix this problem.
Now, there is a difference between being able to capture a well exposed image and judging the image quality by the amount of noise. Of course the camera can use the maximum ISO available and the image will appear bright and well-exposed, but the noise will just ruin the fine details and make the image look bad. The same thing was reported by androidbeat.com who tested the LG G6 dual-camera in both daylight and low-light conditions. You can even check the camera samples yourself. You don't need even to see a full-res samples to see that the image quality is just subpar compared to the Google Pixel, HC U Ultra and Samsung Galaxy S7 edge.
The Sony IMX258 sensor is a relatively small sensor, Type 1/3.06. 13MP is a good resolution but only if you use it on larger sensors, like 1/2.3" ones. Sony's Exmor RS technology can improve the performance but up to some degree. It's not going to make an magic that will turn a low-light image to an image that was taken with much larger pixels. The sensor limitations are obvious by looking at the camera samples.
Of course in daylight it's a completely different story and the LG G6 can capture sharp images with excellent color reproduction. However, users pay a great deal of attention for the low-light performance. People don't want to look at their watch and say: "Oh boy, in one hour I won't be able to shoot anymore"—they want to continue shooting even after the sun sets. Not just that, but to be able to enjoy clear photos without too much image noise.
The wide-angle camera is of course the worst one of the two because of its f/2.4 aperture. You might have seen many sample images that look good, but they have been resized and therefore it's bit hard to notice the noise. In fact, you can get nice low-res shots out of the camera, even the wide-angle one, but these shots will be taken at very high ISO because of sensor's low light gathering capability. Also keep in mind that many resized sample images are also compressed in photo editing software, so the image quality is further reduced.
The LG G6 camera samples also showed me the Sony IMX258 limitations when it comes to dynamic range. I've seen the sample images on androidcentral.com and you can clearly see that the camera is struggling in bringing up the details in the shadow areas. It's not the first time that I've seen this and it made many images look too contrasty. This was especially visible in indoor shots where black just looked almost pure black instead of having shared of black. Details in the shadows and in dark areas were flat and in some areas even non existent.
Many of the LG G6 indoor camera samples that I've seen were even blurry or the moving subjects were blurry because the camera was forced to shoot at relatively slow shutter speeds, therefore making moving objects in the scene appear very blurry.
So overall, the LG G6 has poor image quality in low-light and to be honest, I am not happy with the daylight image quality as well. I blame the low-pixels for that and the wide-angle makes it even worse with its f/2.4 aperture. I was expecting better camera specs in the LG G6, LG's flagship smartphone. It was even better not to have a dual-camera and just one high-performing main camera that can take very high quality images in all lighting conditions. I think that the reason LG has chosen to use the Sony IMX258 Exmor RS sensor is because it's small in size. There was probably no enough space at the back for two large sensors to reside side by side. Anyways, I don't know about you, but I am personally very disappointed with the low-light performance and this is why I posted this in the disadvantage section.