To unlock the Lenovo m10 plus bootloader you will need a windows or mac or linux laptop. You will also need to install adb and you can get the installer from this link,Right click and click save as and save. After that follow these step by step videos. ENABLE OEM UNLOCKING
ALLOW CONNECTING TO TAB WITH ADB
ADB UNLOCK COMMAND
INSTALL ADB ON LAPTOP
Now that we have unlocked the bootloader you might want to install twrp (custom recovery) for many advantages. To do this first you will need to flash an empty dm verity. You can get a empty one here. Flash it by rebooting your tab into fastboot mode from adb and type "fastboot flash vbmeta vbmeta.img". Then flash this boot file here with "fastboot flash boot boot.img" which will root your tab with magisk. Then install magisk from this link.This will be a apk so allow it and then you've succesfully rooted your m10 plus. Now to install twrp on your m10 plus reboot into fastboot from adb and flash this recovery image here with "fastboot flash recovery recovery.img" and then "fastboot reboot ".Lastly go to adb and type adb reboot recovery. And now you've succesfully installed twrp recovery on your m10 plus(2nd gen). Twrp always launches black to open twrp press the power button 2 times and twrp will show up.
To fix that twrp says that the device is encrypted there are actually several steps. First reboot to your device and install any root explorer from the play store. Here is a recommended one Link. Now open root explorer and navigate to the / directory. It will ask for root acces in a popup and click ok. After that open the vendor folder, then from there open the etc folder and click on the fstab.mt6765 and click text viewer. Then at the top right click the pencil icon. From there find the text forcefdeorfbe and replace that with encryptable . After that go back to root explorer and do the same edit in fstab.mt8768 . Then reboot into twrp click on the cancel button for the encrypt password and go on wide , format data, then click advanced wipe in wipe and select Dalvik / Art Cache , chache , and data. Then reboot system. Now setup your lenovo m10 plus once again and your done you succecfully fixed the excryption problem now you can download magisk manager one more time and this time you will already have root so now you have unlocked the full potensiol of your lenovo m10 plus 2nd gen.