It may work well on system which based on LineageOS 20 kernel.
This project based on the kernel of LineageOS 20.0.https://github.com/LineageOS/android_kernel_nubia_msm8998/tree/lineage-20
Here is some modify for supports kernelsu.https://github.com/kindle4jerry/android_kernel_nubia_msm8998-ksu
Backup your boot.img.
Flash the boot.img from this actions to your device.
Install manager.apk from this actions.
If something wrong, please flash your origin boot.img.
LineageOS and all contributors.
KernelSU and all contributors.
xiaoleGun - The script of KerneSU Action. KernelSU_Action