Hello guys,
Since I’ve FP Open OS, I couldn’t use snapchat. I installed FakeGAPPS and microG like in the How to install any app tutorial and that worked partially. But when I tried to connect with my account I had the “failed login” error. It seems snapchat can detect if root is activated even with rootCloak. So I unrooted like in the tutorial I linked and uninstalled Xposed (I don’t know if it’s necessary). Without Xposed I couldn’t use FakeGAPPS so I used Tingle. Then I had not error message when I tried to connect and after the connection I re-rooted (flashing the SuperSu zip with TWRP) and Xposed 
I will improve this ‘tutorial’ with your sharing.