The Samsung Galaxy A9 (2018)'s unique selling point is certainly its back camera with a grand total of four lenses. Nevertheless, the mid-range smartphone surprised us in other disciplines in our tests, keeping pace with other Samsung S series phones.
https://www.notebookcheck.net/Samsung-Galaxy-A9-2018-Smartphone-Review.386081.0.html
Thank you very much for this comprehensive review. I recently bought the A9 2018 for my wife, despite its negative reviews on camera image quality. I have an A8+ and I am totally happy with the images.
I came to the same conclusion like you that images from the A9 2018 main camera were kind of ok but certainly below expectations and even worse than with my A8+.
HOWEVER, I did run a number of test images with a surprising conclusion: SAMSUNG seems to have got the HDR algorithms wrong. With HDR on, the image isn't sharp at all and looks blurry in its details. Definitely a letdown. But when switching HDR to OFF, suddenly details come out sharp and the images are clearly a class better than on my A8+. What does this mean? I will leave HDR on OFF, and only use it eventually in scenes of very high contrast and if sharpness is not so important.
I hope that SAMSUNG will work on its HDR software. The quality could be there, if the HDR would be done right. A new firmware should fix this problem. SAMSUNG, please listen!