[OnePlus 6T  ROMs, Kernels, Recoveries, & Other Dev] Nsane457:
Also, installing opengapps fails.

Relevant recovery.log snippet:

Installing zip file '/sdcard/open_gapps-arm64-9.0-mini-20181130.zip'
Checking for Digest file...
Skipping Digest check: no Digest file found
I:Update binary zip
Verifying package compatibility...
Package doesn't contain compatibility.zip entry
I:Zip does not contain SELinux file_contexts file in its root.
I:Legacy property environment not used in updater.
Archive: /sdcard/open_gapps-arm64-9.0-mini-20181130.zip
inflating: app_densities.txt
Archive: /sdcard/open_gapps-arm64-9.0-mini-20181130.zip
inflating: app_sizes.txt
Archive: /sdcard/open_gapps-arm64-9.0-mini-20181130.zip
inflating: bkup_tail.sh
Archive: /sdcard/open_gapps-arm64-9.0-mini-20181130.zip
inflating: gapps-remove.txt
Archive: /sdcard/open_gapps-arm64-9.0-mini-20181130.zip
inflating: g.prop
Archive: /sdcard/open_gapps-arm64-9.0-mini-20181130.zip
inflating: installer.sh
Archive: /sdcard/open_gapps-arm64-9.0-mini-20181130.zip
inflating: busybox-arm
Archive: /sdcard/open_gapps-arm64-9.0-mini-20181130.zip
inflating: tar-arm
Archive: /sdcard/open_gapps-arm64-9.0-mini-20181130.zip
inflating: unzip-arm
Archive: /sdcard/open_gapps-arm64-9.0-mini-20181130.zip
inflating: zip-arm
Segmentation fault

##############################
_____ _____ ___ ____
/ _ \ | __ \ / _ \ | _ \
| / \ || |__) | |_| || | \ \
| | | || ___/| __/ | | | |
| \ / || | \ |__ | | | |
\_/ \_/ |_| \___| |_| |_|
___ _ ___ ___ ___
/ __| /_\ | _ \ _ \/ __|
| (_ |/ _ \| _/ _/\__ \
\___/_/ \_\_| |_| |___/
##############################

Open GApps mini 9.0 - 20181130

- Mounting /system /vendor

find: /system/system: No such file or directory
ls: /system/system: No such file or directory
- Gathering device & ROM information

***** Incompatible Device Detected *****

This Open GApps package cannot be
installed on this device's architecture.
Please download the correct version for
your device: arm

******* GApps Installation failed *******

- Copying Log to /sdcard

- NO changes were made to your device

Installer will now exit...

Error Code: 64
E:[MTP] MyMtpDatabase::getObjectPropertyList MTP_RESPOSNE_INVALID_OBJECT_HANDLE 3
cp: can't stat '': No such file or directory
ls: /system/system: No such file or directory
cp: can't stat '/system/system/etc/g.prop': No such file or directory
cp: can't stat '/system/system/default.prop': No such file or directory
cp: can't stat '/system/system/build.prop': No such file or directory
cp: can't stat '/vendor/vendor/build.prop': No such file or directory
cp: can't stat '/data/local.prop': No such file or directory
cp: can't stat '/build.prop': No such file or directory
cp: can't stat '/system/system/addon.d/70-gapps.sh': No such file or directory
cp: can't stat '/cache/recovery/log': No such file or directory
__bionic_open_tzdata: couldn't find any tzdata when looking for CST6CDT,M3.2.0,M11.1.0!
__bionic_open_tzdata: couldn't find any tzdata when looking for posixrules!
- Unmounting /system /vendor

mount: mounting /dev/block/bootdevice/by-name/system_a on /system failed: Device or resource busy
Updater process ended with ERROR: 64
I:Install took 8 second(s).
Error installing zip file '/sdcard/open_gapps-arm64-9.0-mini-20181130.zip'0181130.zip'