where to get the magisk flash file.Ok, so please do the following steps:
1. Download the attached vbmeta.img (it's the one of the latest XZ2 stock fw) and place it somewhere on your pc.
2. Copy the Magisk patched kernel (magisk_patched.img) from your device to the same place on your pc.
3. Shut down your device and connect it in fastboot mode with your pc
4. Open a command line from the place you've saved the two files from 1. and 2.
5. Enter the following commands (file by file):
fastboot flash boot_a magisk_patched.img
fastboot flash boot_b magisk_patched.img
fastboot --disable-verity --disable-verification flash vbmeta_a vbmeta.img
fastboot --disable-verity --disable-verification flash vbmeta_b vbmeta.img
(the name of your "magisk_patched.img" could differ, so please use the exact name of yours [mandatory]!)