problem installing Xprivacy : where is the install button? I try to install Xprivacy but I cannot find the install button.
When I click on the app logo on my phone, I get the below screen.

Clicking on check for root, gets me the new message "Device is rooted"
even if I am quite sure it is not.
Probably the missing check mark means that it is not rooted (a bit confusing).

I assume that I first need to root the phone

Correct ?
Your device need to be rooted for Xprivacy to work, be installed properly. Even before installing it, you must install Xposed framework which requires root.

From Xprivacy Github page:


  XPrivacy is built using the Xposed framework, which it uses to tap into a vast number of carefully selected Android functions. 





  Root access is needed to install the Xposed framework.


The process is:


Root your device.
Install Xposed installer.
Install Xposed framework.
Install Xprivacy.