[Samsung Galaxy S9+ Questions & Answers] ultradj83:
Dears,

just got a dual sim S9+ (SM-G965F/DS).

Magisk v16 correctly completes setup via TWRP, but it's then impossible to boot system, it goes bootloop on Galaxy logo.

Nothing to do with 16.1 and 16.2...

Here's installation output:

Installing zip file '/external_sd/Magisk-v16.2(1620).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: /external_sd/Magisk-v16.2(1620).zip
inflating: META-INF/com/google/android/update-binary
inflating: META-INF/com/google/android/updater-script
inflating: addon.d/99-magisk.sh
inflating: arm/magiskboot
inflating: arm/magiskinit
inflating: arm64/magiskboot
inflating: arm64/magiskinit
inflating: chromeos/futility
inflating: chromeos/kernel.keyblock
inflating: chromeos/kernel_data_key.vbprivk
inflating: common/boot_patch.sh
inflating: common/magisk.apk
inflating: common/util_functions.sh
inflating: x64/magiskboot
inflating: x64/magiskinit
inflating: x86/magiskboot
inflating: x86/magiskinit
inflating: META-INF/MANIFEST.MF
inflating: META-INF/CERT.SF
inflating: META-INF/CERT.RSA
************************
* Magisk v16.2 Installer
************************
- Mounting /system, /vendor
- Found boot/ramdisk image: /dev/block/sda10
- Found dtbo image: /dev/block/sda9
- Device platform: arm64
- Constructing environment
Unable to locate class 'com/topjohnwu/magisk/utils/BootSigner'
java.lang.ClassNotFoundException: Didn't find class "com.topjohnwu.magisk.utils.BootSigner" on path: DexPathList[[zip file "/dev/tmp/install/common/magisk.apk"],nativeLibraryDirectories=[/system/lib64, /system/vendor/lib64, /system/lib64, /system/vendor/lib64]]
at dalvik.system.BaseDexClassLoader.findClass(BaseDexClassLoader.java:93)
at java.lang.ClassLoader.loadClass(ClassLoader.java:379)
at java.lang.ClassLoader.loadClass(ClassLoader.java:312)
Exception in thread "main" java.lang.ClassNotFoundException: Didn't find class "com.topjohnwu.magisk.utils.BootSigner" on path: DexPathList[[zip file "/dev/tmp/install/common/magisk.apk"],nativeLibraryDirectories=[/system/lib64, /system/vendor/lib64, /system/lib64, /system/vendor/lib64]]
at dalvik.system.BaseDexClassLoader.findClass(BaseDexClassLoader.java:93)
at java.lang.ClassLoader.loadClass(ClassLoader.java:379)
at java.lang.ClassLoader.loadClass(ClassLoader.java:312)
- Unpacking boot image
MagiskBoot v16.2(1620) (by topjohnwu) - Boot Image Modification Tool
Parsing boot image: [/dev/block/sda10]
KERNEL [28839944]
RAMDISK [6544480]
SECOND [0]
EXTRA [1787904]
PAGESIZE [2048]
NAME [SRPQH16A001KU]
CMDLINE [androidboot.selinux=permissive androidboot.selinux=permissive]
CHECKSUM [1572fc1364f258d10345a47fb99510abd970baaf]
KERNEL_FMT [raw]
RAMDISK_FMT [gzip]
- Checking ramdisk status
MagiskBoot v16.2(1620) (by topjohnwu) - Boot Image Modification Tool
Loading cpio: [ramdisk.cpio]
- Magisk patched image detected
MagiskBoot v16.2(1620) (by topjohnwu) - Boot Image Modification Tool
Loading cpio: [ramdisk.cpio]
Cannot find the file entry [ramdisk.cpio.xz]
Restore [.backup/init] -> [init]
Remove [.backup]
Remove [.backup/.magisk]
Remove [.backup/.sha1]
Dump cpio: [ramdisk.cpio]
- Patching ramdisk
MagiskBoot v16.2(1620) (by topjohnwu) - Boot Image Modification Tool
Loading cpio: [ramdisk.cpio]
Add entry [init] (0750)
Patch with flag KEEPVERITY=[true] KEEPFORCEENCRYPT=[false]
Save SHA1: [026b8c6be08c46e2c8b5c6137f64c6ba8fa44d4a] -> [.backup/.sha1]
Loading cpio: [ramdisk.cpio.orig]
Backup mismatch entry: [init] -> [.backup/init]
Dump cpio: [ramdisk.cpio]
MagiskBoot v16.2(1620) (by topjohnwu) - Boot Image Modification Tool
MagiskBoot v16.2(1620) (by topjohnwu) - Boot Image Modification Tool
- Repacking boot image
MagiskBoot v16.2(1620) (by topjohnwu) - Boot Image Modification Tool
Parsing boot image: [/dev/block/sda10]
KERNEL [28839944]
RAMDISK [6544480]
SECOND [0]
EXTRA [1787904]
PAGESIZE [2048]
NAME [SRPQH16A001KU]
CMDLINE [androidboot.selinux=permissive androidboot.selinux=permissive]
CHECKSUM [1572fc1364f258d10345a47fb99510abd970baaf]
KERNEL_FMT [raw]
RAMDISK_FMT [gzip]
Repack to boot image: [new-boot.img]
KERNEL [28839944]
RAMDISK [6544480]
SECOND [0]
EXTRA [1787904]
PAGESIZE [2048]
NAME [SRPQH16A001KU]
CMDLINE [androidboot.selinux=permissive androidboot.selinux=permissive]
CHECKSUM [1572fc1364f258d10345a47fb99510abd970baaf]
MagiskBoot v16.2(1620) (by topjohnwu) - Boot Image Modification Tool
Cleaning up...
- Flashing new boot image
- Unmounting partitions
- Done
I:Updater process ended with RC=0
I:Install took 13 second(s).

I'm also attaching full TWRP log, I'm returning error

[COLOR="#FF0000"]Failed to mount '/cpefs' (Read-only file system)[/COLOR]

upon TWRP launch.

Any suggestions?

Tks.