You can follow the steps in the link below but use the Bison GT boot.img file from the rom on umidigi's site. I can confirm this works.
*Remember, unlocking your bootloader will cause your phone to be erased.
Here is the short version:
In a nutshell, assuming you have your drivers setup for ADB and Fastboot...on this phone, everytime I go into bootloader mode, I have to goto device manager and set the driver manually to the google bootloader one.
Steps:
- unlock bootloader
- install magisk apk on phone(https://magiskmanager.com/)
- Extract boot.img from stock rom that is installed on your device. https://community.umidigi.com/forum.php?mod=forumdisplay&fid=258
- Copy boot.img over to your phone
- Run magisk app on your phone, click install, click from file, locate boot.img on your phone and start. This will patch that boot.img
- Copy patched boot.img that magisk created from your phone to your PC
- Reboot phone into bootloader mode/fastboot (adb reboot-bootloader)
- Flash patched boot image to boot partition: fastboot flash boot nameofpatchedboot.img
- Reboot into phone and see if it worked.
This will get root working on Bison GT