Until now, Google Camera wasn’t working on the Samsung Galaxy Note 9, but an XDA user was able to get it working. 5.1.018.177470874.41362666_N6_2.5_test.apk which is the last working one of Google camera that fully working on Samsung Galaxy Note 9.
Keep in mind that this is only working on Exynos version and not on Snapdragon version. You can download the working version of Google camera apk from here.
If you have installed previous version of Google Camera, follow steps from 1-7, otherwise follow steos from 2-7.
2.Clean Storage/cache from Device maintenance settings
5.From Settings-Apps-Gcam-Storage Clear cache and Clear data
7.Start Google camera and enjoy.
Nice thing to know is that HDR+, HDR+ enhanced and Portrait mode is fully working in this version.
However, not everything is working and we suggest you to use Google Camera for only fun and non serious projects. For reliable camera, stick to stock Samsung camera where everything is working.
The only “problem” I face is the progression in the notification panel that stay until manual FC, even if HDR is already processed.