[Magisk] DessertArbiter:
twrp didnt give any errors, so it looks like magisk installed correctly:

Installing zip file '/sdcard/Magisk-v19.3.zip'
Checking for Digest file...
I:Update binary zip
Verifying package compatibility...
Package doesn't contain compatibility.zip entry
I:Extracting updater binary 'META-INF/com/google/android/update-binary'
I:Zip does not contain SELinux file_contexts file in its root.
I:Legacy property environment not used in updater.
1022+1 records in
1022+1 records out
1047368 bytes (1022.8KB) copied, 0.006878 seconds, 145.2MB/s
Archive: /sdcard/Magisk-v19.3.zip
inflating: META-INF/com/google/android/update-binary
inflating: META-INF/com/google/android/updater-script
inflating: arm/magiskboot
inflating: arm/magiskinit
inflating: arm/magiskinit64
inflating: chromeos/futility
inflating: chromeos/kernel.keyblock
inflating: chromeos/kernel_data_key.vbprivk
inflating: common/addon.d.sh
inflating: common/boot_patch.sh
inflating: common/magisk.apk
inflating: common/util_functions.sh
inflating: x86/magiskboot
inflating: x86/magiskinit
inflating: x86/magiskinit64
inflating: META-INF/MANIFEST.MF
inflating: META-INF/CERT.SF
inflating: META-INF/CERT.RSA
************************
* Magisk v19.3 Installer
************************
- Mounting system
- Mounting vendor
- Target image: /dev/block/mmcblk0p36
- Device platform: arm
- Constructing environment
- Adding addon.d survival script
Signature is VALID
- Boot image is signed with AVB 1.0
- Unpacking boot image
Parsing boot image: [/dev/block/mmcblk0p36]
HEADER_VER [0]
KERNEL_SZ [13230607]
RAMDISK_SZ [1523456]
SECOND_SZ [0]
EXTRA_SZ [0]
RECOV_DTBO_SZ [0]
DTB [0]
OS_VERSION [9.0.0]
OS_PATCH_LEVEL [2019-02]
PAGESIZE [2048]
NAME []
CMDLINE [console=ttyHSL0,115200,n8 androidboot.console=ttyHSL0 androidboot.hardware=qcom user_debug=30 msm_rtb.filter=0x237 ehci-hcd.park=3 androidboot.bootdevice=7824900.sdhci lpm_levels.sleep_disabled=1 firmware_class.path=/vendor/firmware_mnt/image loop.max_part=7 vmalloc=400M buildvariant=user]
CHECKSUM [70115ff689943eaea519aef375bad91c5184f8af]
KERNEL_DTB [3705999]
KERNEL_FMT [raw]
RAMDISK_FMT [gzip]
Kernel is uncompressed or not a supported compressed type!
- 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=[false]
Remove [verity_key]
Loading cpio: [ramdisk.cpio.orig]
Backup mismatch entry: [init] -> [.backup/init]
Backup missing entry: [verity_key] -> [.backup/verity_key]
Create directory [.backup] (0000)
Add entry [.backup/.magisk] (0000)
Dump cpio: [ramdisk.cpio]
Loading dtbs from [kernel_dtb]
Found fstab in dtb.0000
Found fstab in dtb.0001
Found fstab in dtb.0002
Found fstab in dtb.0003
Found fstab in dtb.0004
Found fstab in dtb.0005
Found fstab in dtb.0006
Found fstab in dtb.0007
Found fstab in dtb.0008
Found fstab in dtb.0009
Found block [vendor] in fstab
Remove pattern [,verify]
Found block [system] in fstab
Remove pattern [,verify]
Found fstab in dtb.0010
Found block [vendor] in fstab
Remove pattern [,verify]
Found block [system] in fstab
Remove pattern [,verify]
Found fstab in dtb.0011
Found block [vendor] in fstab
Remove pattern [,verify]
Found block [system] in fstab
Remove pattern [,verify]
Found fstab in dtb.0012
Found block [vendor] in fstab
Remove pattern [,verify]
Found block [system] in fstab
Remove pattern [,verify]
Found fstab in dtb.0013
Found block [vendor] in fstab
Remove pattern [,verify]
Found block [system] in fstab
Remove pattern [,verify]
Found fstab in dtb.0014
Found block [vendor] in fstab
Remove pattern [,verify]
Found block [system] in fstab
Remove pattern [,verify]
- Removing dm(avb)-verity in kernel_dtb
- Repacking boot image
Parsing boot image: [/dev/block/mmcblk0p36]
HEADER_VER [0]
KERNEL_SZ [13230607]
RAMDISK_SZ [1523456]
SECOND_SZ [0]
EXTRA_SZ [0]
RECOV_DTBO_SZ [0]
DTB [0]
OS_VERSION [9.0.0]
OS_PATCH_LEVEL [2019-02]
PAGESIZE [2048]
NAME []
CMDLINE [console=ttyHSL0,115200,n8 androidboot.console=ttyHSL0 androidboot.hardware=qcom user_debug=30 msm_rtb.filter=0x237 ehci-hcd.park=3 androidboot.bootdevice=7824900.sdhci lpm_levels.sleep_disabled=1 firmware_class.path=/vendor/firmware_mnt/image loop.max_part=7 vmalloc=400M buildvariant=user]
CHECKSUM [70115ff689943eaea519aef375bad91c5184f8af]
KERNEL_DTB [3705999]
KERNEL_FMT [raw]
RAMDISK_FMT [gzip]
Repack to boot image: [new-boot.img]
HEADER_VER [0]
KERNEL_SZ [13230607]
RAMDISK_SZ [1752802]
SECOND_SZ [0]
EXTRA_SZ [0]
RECOV_DTBO_SZ [0]
DTB [0]
OS_VERSION [9.0.0]
OS_PATCH_LEVEL [2019-02]
PAGESIZE [2048]
NAME []
CMDLINE [console=ttyHSL0,115200,n8 androidboot.console=ttyHSL0 androidboot.hardware=qcom user_debug=30 msm_rtb.filter=0x237 ehci-hcd.park=3 androidboot.bootdevice=7824900.sdhci lpm_levels.sleep_disabled=1 firmware_class.path=/vendor/firmware_mnt/image loop.max_part=7 vmalloc=400M buildvariant=user]
CHECKSUM [25248a5a73f723305cbb9f117488f39b77b96386]
- Flashing new boot image
- Sign image with test keys
Cleaning up...
- Unmounting partitions
- Done

edit: i looked at the updater_binary and it seems that this module is looking for /data/adb/magisk/util_functions.sh, which is actually located at /data/magisk/util_functions.sh until first boot, and then it is copied to the first location

i booted once and then rebooted back into recovery and it flashed without issue