Google Camera with HDR+ added can be sideloaded on many 2016-17 Android models
The bottom line? The software provided definite improvements in the processing of photographs shot with these handsets. XDA's theory, after finding references to "PixelXL2" in the code, is that the modifications trick the app into thinking that it is running on a sequel to the Pixel.
Install Google Camera with HDR+ added through the use of this APK file from XDA. Simply click on this link.
And if you want to see how adding HDR+ can improve your photos, click on the slideshow below. You will find alternating images taken by the camera on the OnePlus 3. The first picture in each series uses the regular default software that the phone shipped with. The second image in the series shows how the Google Camera app with HDR+ makes a photo look brighter and clearer.