https://community.myteracube.com/t/advanced-unlock-the-bootloader/78
https://community.myteracube.com/t/advanced-users-only-twrp-recovery-root-for-teracube-2e/1729
https://community.myteracube.com/t/advanced-installing-an-android-image-w-sp-flash/1003
The following guide is how I was able to root my phone. The links provided are the same ones of the forum, if you don't trust me it's okay just download them from the forum :D
download adb and fastboot from here and install
Settings > System > About and tap Build number ten times to unlock Developer Options
turn on OEM unlocking (and debug USB) and plug the phone to the PC (I plugged it in for data transfer)
open adb program (terminal will open) → adb reboot-fastboot (confirm from device if prompt)
if the phone get stuck in fastboot, unplug it, install these drivers and restart PC (NOTE: the drivers are unsigned, I did trust them anyway after reading positive reviews on the forum)
!!! if you can't download the drivers because of virus message, go to your Google Drive, make a copy of the file (you'll see it in "Recent") and download the copy (say Download anyway if it tells you the file contain virus)
run fastboot flashing unlock in the terminal (I did this after plugging the phone back in with it still being "stuck" in fastboot screen)
a confirmation message will be displayed on the phone screen, press Vol+ to accept
if after the message you can't select normal boot with volume key and the phone doesn't respond to commands, run fastboot reboot in terminal
the bootloader is now unlocked (you should see a message when booting the phone, or you can check in Developer Options)