[Google Pixel Questions & Answers] TheArkive:
Found it!!!

Managed to get force-encrypt disabled with just plain old SuperSU!!

In general I was moving too fast and trying to do everything on the phone itself. Not a good idea on Pixel (with all the crazy differences in partitions).

Here's what I tried (overkill method):

(the red stuff is most likely the most important, other stuff you can probably ignore)

revert to stock (flash-all - modified)

---> fastboot set_active a (establishing consistency)

---> fastboot -w --skip-reboot update image-sailfish-xxxx.zip

---> -w formats userdata partition

---> --skip-reboot prevents reboot

---> don't want to boot into OS until after Magisk install - right?

---> the rest is normal ... but finish with ...

---> fastboot set_active a (finish with slot A active)

---> fastboot reboot-bootloader (reboot to bootloader instead of OS)

---> trying to introduce a level of control / I've noticed active slot changing unexpectedly after installing certain packages (SuperSU / Magisk / etc)

fastboot boot twrp.img

set TWRP to sideload mode

adb sideload twrp.zip

adb reboot recovery

---> wipe dalvik / data / system / internal

---> format internal storage (typed "yes")

adb reboot recovery (again)

---> select "don't show this again" / swipe right

---> now you can see TWRP folder in /sdcard directory

---> writing to /sdcard is possible without full boot into OS

adb sideload ROM.zip

---> or copy ROM to phone and install with TWRP

adb sideload twrp.zip

---> or copy twrp.zip to phone and instal with TWRP

adb reboot recovery

install SuperSU

---> slot B now active

adb reboot

---> leave slot B active and reboot

This was done on OctOS ROM (multiple times).

Other than that, isn't it weird that slot B is active after installing SuperSU??? I've tried setting slot = A then rebooting after installing SuperSU but it boot loops until it goes back to TWRP. System must remain in slot B to boot.

Also tried setting active slot A in fastboot, but it boot looped until it finally loaded the OS (still unencrypted). Went back into fastboot to check the active slot, and it was slot = B again.

Slightly off topic, I've noticed that the repository versions of the Android SDK Tools gave me funky results (ie. not up-to-date, fastboot not being able to format userdata / unknown partiton format etc) so I setup SDK tools (tools only) from the Android SDK site and added them to my path.

Currently running:

Android SDK Platform-Tools v25.0.6 (lets me set active slot in fastboot)

I modified the file ~/.profile and added my AndroidSDK location at the end:

PATH="$HOME/AndroidSDK/platform-tools:$PATH"
PATH="$HOME/AndroidSDK/build-tools/25.0.3:$PATH"

Just in case, here's all my UDEV rules (haven't found a list this complete online yet but I needed most of these for the Pixel). Run terminal:

sudo nano /etc/udev/rules.d/android.rules

This will give you the option to create the file "android.rules". Just paste the below in there and close out/save the file.

# fastboot mode
SUBSYSTEM=="usb", ATTR{idVendor}=="18d1", ATTR{idProduct}=="4ee0", MODE="0666"

# ROM booted - debug mode disabled - not listed in "adb devices"
SUBSYSTEM=="usb", ATTR{idVendor}=="18d1", ATTR{idProduct}=="4ee8", MODE="0666"
SUBSYSTEM=="usb", ATTR{idVendor}=="18d1", ATTR{idProduct}=="4ee1", MODE="0666"

# ROM booted - debug mode enabled - charging mode
SUBSYSTEM=="usb", ATTR{idVendor}=="18d1", ATTR{idProduct}=="4ee7", MODE="0666"

# ROM booted - debug mode enabled - photo transfer (PTP)
SUBSYSTEM=="usb", ATTR{idVendor}=="18d1", ATTR{idProduct}=="4ee6", MODE="0666"

# ROM booted - debug mode enabled - file transfer (MPT)
SUBSYSTEM=="usb", ATTR{idVendor}=="18d1", ATTR{idProduct}=="4ee2", MODE="0666"

# ROM booted - debug mode enabled - MIDI mode
SUBSYSTEM=="usb", ATTR{idVendor}=="18d1", ATTR{idProduct}=="4ee9", MODE="0666"

# Pixel - different sideload states
SUBSYSTEM=="usb", ATTR{idVendor}=="18d1", ATTR{idProduct}=="d001", MODE="0666"
SUBSYSTEM=="usb", ATTR{idVendor}=="18d1", ATTR{idProduct}=="d002", MODE="0666"

To close and save:

- CTRL + X

- ENTER to finalize save

(take your time and read the prompts at the bottom of the screen - nano is easy to use)

- reboot when done