I faced an issue that Android R emulator cannot be rooted.
First I launch the Android R emulator ->
/Users/myname/Library/Android/sdk/emulator/emulator -avd emulatorname -no-snapshot -writable-system
Then I execute the commands:
adb shell su mount -o rw,remount /system
and get the error -> mount: '/system' not in /proc/mounts
My other attempt also fails, the emulator becomes not responsive after the last command:
adb root adb remount adb reboot