[Xperia Tablet Z Original Android Development] rcurious:
If you experience a bootloop after flashing Magisk, follow these steps:

1. Extract the file `lineage-20.0-xxxxxxxx-UNOFFICIAL-pollux_windy.zip`. Inside, you will find `boot.img`. Ensure that the version of LineageOS you have installed matches the version of the firmware `boot.img` you extracted. It has to be the same firmware zip file - in simple words.

2. Make a USB connection between your tablet and computer.

3. Enter fastboot mode on the tablet using its buttons.

4. On your PC, open a command prompt or terminal from the directory where `boot.img` is located and enter the following command:

fastboot flash boot boot.img

If the command prompt writes 'waiting...' or something similar, check the Windows Device Manager. If there's a yellow exclamation mark, you may need to install the required USB drivers for debugging. Or you not entered fastboot mode. It has to be constant blue LED on the tablet.

5. The tablet should now boot normally.

Note: I experienced boot loops with Magisk versions 26.4, 26.3, 26.2. Only Magisk 26.1 installed successfully using TWRP and allowed me to gain root access.

The only one issue I have with this ROM is the lack of audio over Bluetooth.

Here is proper install log of Magisk 26.1.

Magisk 26.1 Installer
***********************
- Mounting /system
- Device is system-as-root
- Mounting /apex/com.android.adbd
- Mounting /apex/com.android.adservices
- Mounting /apex/com.android.appsearch
- Mounting /apex/com.android.art
- Mounting /apex/com.android.btservices
- Mounting /apex/com.android.conscrypt
- Mounting /apex/com.android.extservices
- Mounting /apex/com.android.i18n
- Mounting /apex/com.android.ipsec
- Mounting /apex/com.android.media
- Mounting /apex/com.android.media.swcodec
- Mounting /apex/com.android.mediaprovider
- Mounting /apex/com.android.neuralnetworks
- Mounting /apex/com.android.ondevicepersonalization
- Mounting /apex/com.android.os.statsd
- Mounting /apex/com.android.permission
- Mounting /apex/com.android.resolv
- Mounting /apex/com.android.runtime
- Mounting /apex/com.android.scheduling
- Mounting /apex/com.android.sdkext
- Mounting /apex/com.android.tethering
- Mounting /apex/com.android.tzdata
- Mounting /apex/com.android.uwb
- Mounting /apex/com.android.wifi
- System-as-root, keep dm/avb-verity
- No vbmeta partition, patch vbmeta in boot image
- Target image: /dev/block/mmcblk0p17
- Device platform: armeabi-v7a
- Constructing environment
- Adding addon.d survival script
- Unpacking boot image
- Checking ramdisk status
- Stock boot image detected
- Patching ramdisk
- Repacking boot image
- Flashing new boot image
- Unmounting partitions
- Done
Updating partition details...
- done

And here is Magisk 26.4 install log

Magisk 26.4 Installer
*******************

- Mounting /system
- Device is system-as-root
- Legacy SAR, force kernel to load rootfs
- No vbmeta partition, patch vbmeta in boot image
- System-as-root, keep dm-verity
- Target image: /dev/block/mmcblk0p17
- Device platform: armeabi-v7a
- Constructing environment
- Adding addon.d survival script
- Unpacking boot image
- Checking ramdisk status
- Stock boot image detected
- Patching ramdisk
- Repacking boot image
- Flashing new boot image
- Unmounting partitions
- Done