[OnePlus 5 ROMs, Kernels, Recoveries, & Other Devel] wartomato:
We merged File Based Encryption (FBE) and Treble changes (Firmware 5.1.5)

This means that a few files and steps are needed from the users (YOU!) for being able to flash the next update.

Yes, you will need an external storage, so a PC or an USB stick (OTG).

For current users (on Firmware 5.1.4 and the latest build) the following files are needed:

The latest ROM zip of course (so, a build of 20180903 or later!)

Latest treble compatible TWRP 3.2.3, which is currently NOT the official one:

https://sourceforge.net/projects/ch...-20180822-codeworkx-cheeseburger.img/download

Stable Treble compatible firmware (currently 5.1.5 as of writing):

https://sourceforge.net/projects/ch...firmware/firmware_5.1.5_oneplus5.zip/download

just for the case of a revert, download the 5.1.4 firmware too:

https://sourceforge.net/projects/ch...firmware/firmware_5.1.4_oneplus5.zip/download

If you want (I did not do it, btw) and recent version of GApps, like openGApps Mini from here: https://opengapps.org/

(This means Platform: ARM64, Android: 8.1, Variant: mini)

Additionally for root, please download Magisk (17.1 as of writing, which fixes for example fastboot issues on OP5's):

* App/APK: https://github.com/topjohnwu/Magisk/releases/download/manager-v5.9.1/MagiskManager-v5.9.1.apk

* flashable ZIP for TWRP: https://github.com/topjohnwu/Magisk/releases/download/v17.1/Magisk-v17.1.zip

* flashable Uninstaller for TWRP: https://github.com/topjohnwu/Magisk/releases/download/v17.1/Magisk-uninstaller-20180901.zip

Note: The uninstaller and zip for flashing in TWRP were not needed in my case!

Steps and precautions I took to update (which should work for most users):

Charge up the phone!

As a precaution it might be a good idea to remove any Lockscreen security like PIN/Pattern and set it to "Swipe".Copy the files above to the aicp_ota folder on the internal storage for easy access to them.

Reboot to recovery and flash the recovery from above before beginning!

After reboot, I made sure all accounts (Settings!) were synced by hand, made sure I made backups for e.g. WhatsApp chats, SMS/MMS, Contacts, Settings, Scores from games, Settings for my custom launcher, etc.

Some of these are not necessary, but always good to have done it. Additionally make sure you have the APKs of apps that you did not install from the Google Play Store at hand or saved somewhere like your Download folder.

Reboot to the recovery and make a complete backup (except "Cache" and "Vendor"). Then reboot back to the System.

Backup your data from the internal storage (media like pictures, files, documents, etc.) AND the TWRP folder (!) by copying to PC or the USB-stick.

Note: The folder "Android" is not needed, so you might leave it out, if you need to save some space on your external storage device.

Reboot to recovery and flash the firmware 5.1.5. Flash the Magical uninstaller! Clean the Cache/Dalvik. Then select from TWRP to reboot to recovery.

In recovery again, wipe the device ("factory reset") without internal storage. Don't reboot.

Now flash the ROM zipfile (only that one!) and wait for it to complete. Don't reboot.

Note: If flashing fails (e.g. showing "Error 7") stop it. There are two options now. First is reflash 5.1.4 firmware and your 'old' build. Second option would be to continue with the next step, format data and sideload the ROM zipfile or copy it to internal storage and flash it.

Select "Wipe" again and chose "Format data" to format the data partition (internal storage).

Reboot. Device might show the TWRP welcome screen and reboot again. Wait until the boot finishes.

It is recommended to set up a PIN with 4 digits, if the first screen after boot recommends it. Set your device up normal afterwards, by e.g. choosing "restore from previous backup". This will take some time as. Register Fingerprints or whatever as you want, during the setup...

Note: You are NOT rooted at this moment!

After completing the procedure, go to settings and make sure you enable Developer settings (Settings -> About Phone -> Tap build number 7 times). Go into the developer settings and enable "Advanced Reboot" and "USB debugging" in there.

Once done, copy back your data you previously backup up to the internal storage. Install the apks you want from that backup that are not restored from the Play Store.

Install Magisk Manager App, if you want to continue rooted. Open it, tap "keep "force encryption" " (make sure it is actived) and chose "Install" and then chose "Restart" after the install finishes. The phone will reboot.

After the reboot, please mind that you will now have to enter a) the PIN for the SIM AND b) the PIN for the phone to unlock.

Note: The unlock PIN is also needed every time you reboot to recovery. It must be entered there to decrypt the internal data from now on!

Set up Magisk as of your liking (Magisk Hide, Superuser, etc.) and continue with restoring or setting up your apps (again!).

Last notes:

As we hopefully did nothing wrong, THERE IS NO WAY TO GET AROUND THE ENCRYPTION PROCESS ("Force Encryption")!

There are no real 'speed' differences using the device encrypted.

The only real change on usage would be that you have to enter the PIN, if a fingerprint or face on unlock is not recognized...

Very last note:

IF everything goes wrong during this process: The TWRP works with older ROM builds too. Just reflash the the 5.1.4 firmware, "format data" again and flash the ROM from 20180827 again and restore your data partition. ;)

I recommend for now to flash the Magisk zipfile (if you use 16.7) after EVERY ROM update in TWRP, to ensure root sticks! IT seems Magiak 17.1 sticks.