You have the Mi 8 non lite, non SE? |
enabling the aux camera as you did is all you need for using the tele lens. Maybe the app needs a restart after changing this seeing (as it does when you change libs and/or camera setting.
The app will do a restart itself but I prefer to force stop it and newly start it as otherwise at least the EXIF data can be wrong (e.g. switching from Pixel III to Nexus 6P it still shows Pixel III although it seems to use the Nexus setting).
Unfortunately the usage of the zoom lens is not shown, it switches between normal/tele - front/selfie - zoom - front - tele and so on. You have to look yourself at the image area to see which lens is currently active.