Can't install System apps from unofficial channel

[SimonLPE]

I tried to install new system launcher with new full screen gesture which find on chinese mi forums
And when I tried to installed it "Can't install System apps from unofficial channel" appears
Some people suggested use default browser and file manager to install it, but no luck...
Can somebody solve this, tHANKS

 

[Igor Eisberg]

Nothing to solve, when it's not a problem, but rather the intended behavior.
You're not supposed to touch system apps, else you would break the intended functionality, features and analytics/tracking patches.