[Update: November 6, 2018]
Google Camera Port with Night Sight Now Available for OnePlus 6/6T
The modded Google Camera app for the OnePlus 6 brought HDR+ and Motion Focus, but it lacked the Night Sight mode.
XDA senior member Arnova8G2, who created the original Google Camera mod, has now successfully enabled the Night Sight mode on a new build which is compatible with the OnePlus 6 as well as the OnePlus 6T.
The new mod for the OnePlus duo also has the HDR+ mode in the active state.
How to Download Google Camera Mod for OnePlus 6/6T?
You can download the Google Camera mod for the OnePlus devices from the link below: