[Android Q&A, Help & Troubleshooting] rolland.arriza:
Lenovo Phab PB1-750M 6.0.1 Marshmallow

Before anything else, make backup.

*UPDATED "Drivers" link: (June 17, 2023)

What's in the guide?

(A) Rooting

(B) Installing TWRP custom recovery

(C) Installing Xposed framework

Firmware:

These are full OTA. Install via recovery. Latest is PB1-750M_S000675_170107_ROW. Links from this forum.

PB1-750M_S000675_170107_ROW

PB1-750M_S000660_160930_ROW

***Some users (including me) had encountered an error ("Permission denied") on OTA update PB1-750M_S000660_160930_ROW_TO_PB1-750M_S000675_170107_ROW. If you can't update to the latest, just install the PB1-750M_S000675_170107_ROW full OTA.

Requirements:

(a) Driver. This should be installed by your device and can be found on CD Drive when you connect your device. Install "LenovoUsbDriver_autorun_1.1.30_user.exe" found on the link.

(b) Latest ADB and Fastboot (I recommend Minimal ADB and Fastboot).

(c) Download SevenMaxx TWRP image. Thanks estanenmi for the link.

(d) Download SuperSU binaries. This is v2.68. You could try the latest or just update it after successful install.

(e) Unlock the bootloader. On your device, go to Settings > Developer Options > Allow OEM Unlocking. Then reboot into bootloader via terminal/cmd: adb reboot bootloader. When in fastboot mode, type in terminal/cmd: fastboot oem unlock-go.

***fastboot oem unlock-go will restore the device to factory settings.

Rooting:

(a) Place the TWRP image on the root directory of Minimal ADB and Fastboot (or where your adb and fastboot is located)

(b) Copy the SuperSU zip file on your device

(c) Go to terminal/cmd: adb reboot bootloader

****You can also go to fastboot via "volume down + power" buttons.

(d) Go to terminal/cmd: fastboot boot twrp.img

****If you have flashed a custom recovery, you can install via recovery. The code above just temporarily boot the TWRP image.

(e) Then: fastboot reboot

(f) Navigate the TWRP. I strongly suggest to make a "backup" first.

(g) In TWRP, go to "Install" > locate and select the SuperSU.zip. Swipe to confirm.

(h) Reboot after installation. Your device may reboot a few times.

(i) Download root checker to verify.

*SuperSU app may update and may require to update su binaries.

*If SuperSU installation fails, boot the TWRP.img again and restore (if you have created a backup ).

*You could try installing the SuperSU listed above if your device is on bootloop due to unsuccessful rooting (worked for me).

*I haven't looked for possible problems pre and post rooting - always do backup.

Screenshot

Installing TWRP (custom recovery):

I haven't found any official custom recovery for this device. The custom recovery TWRP by SevenMaxx (from a russian forum) works. (install at your own risk). You can install the custom recovery via fastboot.

****If you only need root access, I suggest that you temporarily boot the TWRP to install SuperSU. It's better to wait for the official custom recovery for the device.

(a) First, the device's bootloader must be unlocked. Check the requirements on how to unlock bootloader.

(b) Configure your device again and enable USB debugging and OEM unlocking.

(d) Go to terminal/cmd: adb reboot bootloader

(e) Then: fastboot flash recovery twrp.img

(f) Device will reboot.

(g) Check the new recovery options via (1) Volume Up + Power button; or (2) adb reboot recovery

Installing Xposed framework (manual):

Please check the official thread for xposed on LL/MM. The device has an ARM architecture and is running on android 6.0.1 (sdk23). Download the latest xposed framework (.zip) here (current latest v87) and xposed installer (.apk) here.

(a) Your device must have root access. Follow the guide on how to root the device.

(b) Install the Xposed (.apk). ***You can install the framework via the Xposed app.

(c) Copy the *.zip file on your device.

(d) Boot your device into recovery (im using the TWRP used in this guide) and install the xposed *.zip.

(e) Reboot. On startup ("Android is starting" message), the device will "optimize applications" and could take a long time.

(f) Check the xposed app download some modules.