See updated guide how I upgraded to Android Q/10 here
Before you do anything listed below Please Please Please understand that if done incorrectly you will break your tablet and make it unusable. It is also important to note that not all devices with this name is the same, I have only tested this on the X704L but it would probably work the same on X704F as well, do not try this on any other tablets without first verifying with the creators that it works on your tablet.
I am writing this guide mainly as a reference for my future self so it will be on a level where you already have to know the basics of these things. If you don’t understand the steps in my guide, please head over to the XDA thread instead and have a look at their instructions for installing the OS.
I have made backups of all the files I mention in this guide as I know this type of thing tends to disappear after a few years. If any of the files / sites I link to has disappeared let me know and I will share these files. I will only share my copy of the files once the official ones are gone as I want the creators/maintainers to get the credit they deserve. By going the official route you also make sure you always get the latest versions.
The following are the steps I followed when I did it earlier this week, please note that newer versions might require different steps.
I started by installing Minimal ADB and Fastboot on my computer, this was to allow me to send commands to the tablet easier.
Next I enabled developer options on the tablet and enabled OEM unlock and USB debugging, I connected the tablet to the computer and ran the following command
adb reboot bootloader
This put the tablet in the bootloader mode where you only see a Lenovo logo. Once I saw the logo I ran another command. Keep in mind that this command will factory reset the device.
fastboot oem unlock-go
As the device is now factory reset I had to enable USB debugging again and after that it was time to start downloading the stuff I was going to install.
First off was TWRP. One thing to keep in mind here is that the TWRP states that it is for X704F and not X704L. The version I used worked fine on the L but make sure to verify that newer versions do this as well before flashing. The version I used was twrp-3.3.1-0-X704F.img.
Next it was time to download the ROM, when I write this there is only one Pie ROM available for the tablet and that is an Unofficial version of Lineage OS 16 maintained by yener90. I used the version that was released 20190609
Since Lineage comes without any Google software I also downloaded the Micro GApps pack from The Open GApps Project. Make sure to check Arm64, Android 9 .0 and Micro before hitting download.
The last thing I needed to download for now was Magisk. I downloaded the latest stable version which at the time I write this is 19.3. When I was at it I also downloaded the Magisk Manager APK as that would be required later.
Once everything was downloaded I put a copy of everything both in the root of the internal storage and at the root of an external SD card. Then I ran the command
adb reboot bootloader
Once again, remember that this will only show you the Lenovo logo, when I saw it I ran the command
fastboot flash recovery twrp-3.3.1-0-X704F.img
Once flashed I used the volume buttons to navigate the menu at the top of the screen, wen it said Recovery Mode I used the power button to select it. This booted TWRP where I selected that I want to write to system.
The first thing I did now was make a backup of everything to an external SD card so I always have a way back if I want to.
Now it was time to clean out the old Android, hit wipe but don´t use the slide, instead hit format data and type yes. Once done, hit the back button and go to advanced wipe. Check Dalvik/ART Cache, System and Cache then swipe to wipe them. Go back to the main menu and reboot into recovery. If it asks if I want to install a TWRP app I always say no.
Once back in TWRP I began by flashing the ROM, then GAPPS and lastly Magisk, then I rebooted into system. Once again say no if it asks for installing a TWRP app.
Now I went through the setup of the tablet and once done I installed the Magisk Manager apk that I downloaded earlier.
Insie Magisk manager I headed to the settings and made sure Magisk Hide was enabled and also enabled that Magisk manager itself should be hidden (this is done by regenerating a package with a random name, cool!)
I headed to Google Play and installed the app “Termux”, in my case it was version 0.72.
Then I went back to magisk manager and installed the module “Busybox for Android NDK version 1.30.1. When it was installed I rebooted the device.
Now I headed over to XDA again and downloaded “MagiskHide Props Config” version 4.0.3. Then I went back to Magisk manager and installed this as a new module and rebooted the device.
When the tablet was back up I opened up Termux and typed su and hit enter, gave it root permissions and then typed props. I followed the menu that was started like this
Edit device fingerprint -> pick a certified fingerprint -> Lenovo -> Lenovo K6 Note (7.0) -> yes for reboot.
When the device was back up I ran the SafetyNet check inside Magisk Manager and saw that everything was green but when I tried to search for Netflix on Google Play it still didn’t show up. To fix this I headed in to the tablets settings, then apps, show system apps. Then clear all data for Google Play Services and Google Play. Now I rebooted the device one final time and then it was done.
The tablet is now running Android Pie and passes SafetyNet. One last thing to keep in mind is that SafetyNet is always updated so this will probably break in the future and then Magisk will probably update to fix it again etc etc. If always passing SafetyNet is really important to you I recommend looking for a new tablet with official updates.