[Essential Phone ROMs, Kernels, Recoveries, & Other] Lakino:
It actually took me quite some time to fully understand the process and to parse together the whole process from multiple websites and postings. Posts like sruel3216's above may offer enough hints for someone well studied in the art of rooting and flashing, it doesn't offer much, if at all, to a newbie. All that jargon is basically Greek to newbies and most likely only serve to confuse.

I'm going to spend the time and effort to write something longer and try to explain more for newbies.

WARNING: I do NOT know if I've lost touch in TWRP as I never flashed TWRP recovery. I did NOT use TWRP at all for this upgrade process. So it's possible I've lost touch in TWRP. I simply don't know. If TWRP access is critical for you, then do NOT follow my process. You may lose touch access in TWRP.

For my specific situation, what I was most confused about was whether having EX Kernel installed was going to affect my upgrade from August build 91 to Sept Build 36. And yes it does.

Because I had installed EX Kernel 3.07 on August build 91, I had changed stock boot.img. Therefore, I could not just upgrade by downloading the update on the phone. It simply won't work because I didn't have stock boot.img.

So the very first step for those with EX Kernel installed is to revert back to stock boot. If you followed EX Kernel install instructions from his website, you should have originally backed up a boot.img. You need revert back to stock boot.img. If you have EX Manager, you can simply flash the boot.img from within EX Manager and it will revert you back to your stock boot.img. Once you do that, you will be UNrooted. I repeat, once you do that, you will be UNrooted. If you don't have EX Manager, then in order to revert back to stock boot.img, you'll need to boot into bootloader and issue command:

fastboot flash boot boot.img

This will flash the stock boot.img back to your phone. After flashing, you will be UNrooted.

If you don't have a backup copy of the stock boot.img, then you can get it here:

https://drive.google.com/drive/folders/114dl75ItxUWWbGnmdYsF2o8-ouryFkXx

Download the file "PIE-9.0-091-JUL-AUG.img"

This is the stock boot image for August build 91. Just rename it to "boot.img".

Once you have your phone back to stock boot, now you can receive OTA update. I advise NOT upgrading to latest build through your phone's upgrade process. Download the OTA image and sideload the OTA file yourself. Read the information from Essential website and follow their instructions.

https://www.essential.com/developer/current-builds

Make sure to download

September 2018 Release | Android 9 Pie, Release 2 - PPR1.180905.036 |

Download (OTA)

You do NOT want the Fastboot file.

Once you've sideloaded the OTA update and it completes upgrading -- it takes a while -- then boot up your phone and let it continue to fully update. This is the time to check to make sure touch works when your phone is all booted up.

If touch works when your phone is all booted up into Sept update 36, then you're upgraded. :good: Yay! Now you just need to root if you want that.

Rooting is extremely simple. Just download sept_patched_boot.img that clsA shared in post #618:

https://androidfilehost.com/?fid=1322778262903999803

You need to flash this patched boot.img in bootloader mode.

Reboot into Bootloader. Issue this command:

fastboot flash boot sept_patched_boot.img

This will update your boot.img with a patched magisk rooted boot.img. You will be rooted.

Now reboot and verify root. You should be rooted. If you had Magsik Manager before, you should still have it. You may need to re-download some of your modules if you have any. I had to redownload youtube vanced but otherwise everything was as before. All the apps I gave root access to previously was still set in MM.

If you have EX Manager, update to latest 3.08 EX Kernal within EX Manager. If you don't have EX Manager, follow instructions posted in OP of this thread to install/update to latest 3.08 EX Kernal.

That's it. You should be fully upgraded to Pie Sept build 36 with EX Kernal 3.08, like me. :fingers-crossed::good::victory:

Because I never touched TWRP through this process, I did NOT de-activate fingerprint or PIN security. My fingerprint sensor works.

The process sounds complicated to newbies -- I completely get that. But once you fully understand the process flow and why you're doing each of these steps, and you actually execute this process, it turns out to be rather simple. Or at least I thought it was very simple once I started executing each step.

I do NOT know if I've lost touch in TWRP as I never flashed TWRP recovery. I did NOT use TWRP at all for this upgrade process. So it's possible I've lost touch in TWRP. I simply don't know. If TWRP access is critical for you, then do NOT follow my process. You may lose touch access in TWRP.

Hope this long post helps the newbies. If you appreciated my post, please push the thank button below. ;)