I was looking in my Nova setting for the Note 5 and couldn't find anything for double tap to wake.
After a little searching, I was able to find this app and it seems to work pretty good? Give it a shot and see what you think?
https://forums.androidcentral.com/e...details?id=com.jamworks.knockz&token=Pbfkii8q
This app does not lock or turn off your screen...It just displays black color on screen so you don't see anything...Will kill battery.