[OnePlus 7T Guides, News, & Discussion] gruuolq:
Me too: booting the european version boot.img via fastboot works (the indian(?) version pre-patched image from this thread has no working wifi), but patching it with the latest canary version of Magisk and booting the magisk_patched.img results in a Qualcomm carshdump screen.

Contents of magisk_install_log_2019-10-19T12:20:18Z.log:

- Device platform: arm64-v8a

- Copying image to cache

1618+0 records in

1618+0 records out

1656832 bytes (1.5 M) copied, 0.012783 s, 124 M/s

1085+1 records in

1085+1 records out

1111628 bytes (1.0 M) copied, 0.010180 s, 104 M/s

- Unpacking boot image

Parsing boot image: [/data/user_de/0/com.topjohnwu.magisk/install/boot.img]

HEADER_VER [2]

KERNEL_SZ [35268624]

RAMDISK_SZ [776110]

SECOND_SZ [0]

RECOV_DTBO_SZ [0]

DTB [1918160]

OS_VERSION [10.0.0]

OS_PATCH_LEVEL [2019-09]

PAGESIZE [4096]

NAME []

CMDLINE [androidboot.hardware=qcom androidboot.console=ttyMSM0 androidboot.memcg=1 lpm_levels.sleep_disabled=1 video=vfb:640x400,bpp=32,memsize=3072000 msm_rtb.filter=0x237 service_locator.enable=1 swiotlb=2048 loop.max_part=7 androidboot.usbcontroller=a600000.dwc3 buildvariant=user]

CHECKSUM [62ccd81eb824905aac2a03742ccc8901aa33a49c]

KERNEL_FMT [raw]

RAMDISK_FMT [gzip]

- Checking ramdisk status

Loading cpio: [ramdisk.cpio]

- Stock boot image detected

- Backing up stock boot image

- Patching ramdisk

Loading cpio: [ramdisk.cpio]

Add entry [init] (0750)

Patch with flag KEEPVERITY=[false] KEEPFORCEENCRYPT=[true]

Found fstab file [fstab.qcom]

Found pattern [,avb=vbmeta_system]

Found pattern [,avb]

Found pattern [avb]

Found pattern [avb]

Found pattern [avb]

Found pattern [avb]

Found pattern [avb]

Found pattern [avb]

Found pattern [,avb=vbmeta_system]

Found pattern [,avb]

Found pattern [,avb]

Loading cpio: [ramdisk.cpio.orig]

Backup mismatch entry: [fstab.qcom] -> [.backup/fstab.qcom]

Backup mismatch entry: [init] -> [.backup/init]

Create directory [.backup] (0000)

Add entry [.backup/.magisk] (0000)

Dump cpio: [ramdisk.cpio]

Loading dtbs from [dtb]

Found fstab in dtb.0000

Found entry [vendor] in fstab

Found pattern [,avb]

Found entry [odm] in fstab

Found pattern [,avb]

Found fstab in dtb.0001

Found entry [vendor] in fstab

Found pattern [,avb]

Found entry [odm] in fstab

Found pattern [,avb]

Found fstab in dtb.0002

Found entry [vendor] in fstab

Found pattern [,avb]

Found entry [odm] in fstab

Found pattern [,avb]

Found fstab in dtb.0003

Found entry [vendor] in fstab

Found pattern [,avb]

Found entry [odm] in fstab

Found pattern [,avb]

- Patching fstab in dtb

Patch @ 01C4DCC4 [736B69705F696E697472616D667300]->[77616E745F696E697472616D667300]

- Repacking boot image

Parsing boot image: [/data/user_de/0/com.topjohnwu.magisk/install/boot.img]

HEADER_VER [2]

KERNEL_SZ [35268624]

RAMDISK_SZ [776110]

SECOND_SZ [0]

RECOV_DTBO_SZ [0]

DTB [1918160]

OS_VERSION [10.0.0]

OS_PATCH_LEVEL [2019-09]

PAGESIZE [4096]

NAME []

CMDLINE [androidboot.hardware=qcom androidboot.console=ttyMSM0 androidboot.memcg=1 lpm_levels.sleep_disabled=1 video=vfb:640x400,bpp=32,memsize=3072000 msm_rtb.filter=0x237 service_locator.enable=1 swiotlb=2048 loop.max_part=7 androidboot.usbcontroller=a600000.dwc3 buildvariant=user]

CHECKSUM [62ccd81eb824905aac2a03742ccc8901aa33a49c]

KERNEL_FMT [raw]

RAMDISK_FMT [gzip]

Repack to boot image: [new-boot.img]

HEADER_VER [2]

KERNEL_SZ [35268624]

RAMDISK_SZ [1014077]

SECOND_SZ [0]

RECOV_DTBO_SZ [0]

DTB [1918128]

OS_VERSION [10.0.0]

OS_PATCH_LEVEL [2019-09]

PAGESIZE [4096]

NAME []

CMDLINE [androidboot.hardware=qcom androidboot.console=ttyMSM0 androidboot.memcg=1 lpm_levels.sleep_disabled=1 video=vfb:640x400,bpp=32,memsize=3072000 msm_rtb.filter=0x237 service_locator.enable=1 swiotlb=2048 loop.max_part=7 androidboot.usbcontroller=a600000.dwc3 buildvariant=user]

CHECKSUM [d218e44ae0bdc9a82fba43738a31b0b8a4e349fb]

****************************

Output file is placed in

/storage/emulated/0/Download/magisk_patched.img

****************************

- All done!

EDIT: After re-reading the logfile, I found the entry "KEEPVERITY=[false]". So I obviously forgot to check the "Advanced Setting" named "Preserve AVB 2.0/dm-verity". After checking this option and repeating everything I now have a rooted and working european 7t! :)