OnePlus 6 Enchilada LineageOS Update instructions 16.0 -> 17.1

gistfile1.txt

# install device tree for Android P - this is needed for TWRP P to run
fastboot flash dtbo dtbo_op6-P.img (https://kremowka.xyz/files/op_dtbo/dtbo_op6-P.img)
# boot TWRP P - can take a few seconds to come up. TWRP P is needed to install the stock image
fastboot boot twrp-3.3.1-18-enchilada-Pie-mauronofrio.img (https://sourceforge.net/projects/mauronofrio-twrp/files/Enchilada/twrp-3.3.1-18-enchilada-Pie-mauronofrio.img/download)
# upload the stock image installer
adb push <oos10> /tmp (https://oneplus.com/support/softwareupgrade)
# install the stock image. this is needed to get the device tree for Android Q
adb shell twrp install /tmp/<oos10>
adb reboot bootloader

# boot TWRP Q - can take a few seconds to come up. TWRP Q requires the device tree that was installed in the step above.
# if the wrong device tree is installed, TWRP Q doesn't start and simply hangs.
fastboot boot twrp-3.3.1-18-enchilada-Q-mauronofrio.img (https://sourceforge.net/projects/mauronofrio-twrp/files/Enchilada/twrp-3.3.1-18-enchilada-Q-mauronofrio.img/download)
# make sure that the a/b partitions are all up to date
adb shell twrp sideload
adb sideload copy-partitions.zip (https://androidfilehost.com/?fid=8889791610682929240)
# sideload lineage OS. this can only be done from TWRP Q (or from the lineageOS recovery, which also requires the new device tree)
adb shell twrp sideload
adb sideload <lineage>
adb reboot bootloader

# optional step: sideload the google apps (if you previously had google apps installed)
# This must be done _before_ lineageOS is launched for the first time
fastboot boot twrp-3.3.1-18-enchilada-Q-mauronofrio.img
adb shell twrp sideload
adb sideload <gapps>
adb reboot