Notification type (notification vs indication) is now supported on ChromeOS. Android and Windows provide similar APIs:

https://docs.microsoft.com/en-us/uwp/api/windows.devices.bluetooth.genericattributeprofile.gattcharacteristic.writeclientcharacteristicconfigurationdescriptorasync#Windows_Devices_Bluetooth_GenericAttributeProfile_GattCharacteristic_WriteClientCharacteristicConfigurationDescriptorAsync_Windows_Devices_Bluetooth_GenericAttributeProfile_GattClientCharacteristicConfigurationDescriptorValue_

https://developer.android.com/guide/topics/connectivity/bluetooth-le#notification

Thus, the same type of support should be enabled on these platforms.