Rooting Doogee Mix is simple.You need to install the TWRP then flash superSu
Downloads
Download TWRP Recovery
Download
SuperSU Zip by Chainfire from here (V2.82)
or you can download latest
Magisk
Download Latest version of
SPFlash Tool for Windows here.
Now follow the guide to Install TWRP using Sp flash tool >
How to install TWRP using SP flash tool On MediaTek devices
Note: Find the Scatter File from the downloaded TWRP zip file, which you have downloaded. Rename the TWRP (.img) file to recovery.img. Now, on the flash tool interface, navigate and select the scatter file and At this stage, just leave the recovery as ticket/ checked. Now, at the location tab, click on the storage location field of the recovery and search and browse for the custom recovery image file which is device-specific
Now follow this guide Install/Flash
Magisk or
SuperSu to get your device rooted.