A few videos recently posted to YouTube took a closer look at the Doogee Mix and found that the dual-camera setup actually uses one camera and some software tricks to simulate effects that would otherwise require two camera modules. The problem seems to be rampant among cheap Chinese smartphones.
https://www.notebookcheck.net/Dual-camera-dupe-some-smartphones-with-dual-camera-setups-only-have-one-camera-enabled.247104.0.html