Cannot Open Dev Menu on Xiaomi Devices

I get Xiaomi Mi 8 and, after many hours I have discovered how show the dev menu.

The problem, in this device, is that when you send the command:

adb shell input keyevent 82

is the same that perform a click "menu button" on device.

In brief, if you want to show dev menu on newest devices with miui, you must perform a "long click" on the menu button (NOT A "SIMPLE CLICK")

All the best!

For xiaomi devices, you need to enable popup permission from security->permissions->app name -> popup

Source: https://github.com/facebook/react-native/issues/2754#issuecomment-140815500

On my Redmi 4X i need to hold the "menu" button to open The Dev Menu options.

To verify this option, you can go to: Settings --> Additional config --> Buttons and gestures shortcuts --> Show menu

PS: As palaniraja said, you need to enable popup permission as well.