[OnePlus 7 & 7 Pro Cross Device Development] nethunterkali:
Already know what I did wrong:

-wrong twrp install (did't understood well slot_a ,_b)

I wrote:

This is wrong method.

At the moment. I have sucessfully installed nethunter on almost all from 9.54.BA-10.0.2.BA.

Here are working sets for me:

*****************************9.5.4.GM21BA*********************************************
-install stock recovery guacamole msm tool "9.5.4.GM21BA" & finish android setup
-unlock developer options, unlock bootloader-here automatic wipe & finish android setup
-unlock developer options, reboot to bootloader, flash "twrp-installer-3.3.1-4-guacamole.img" by fastboot, reboot to recovery
-install "twrp-installer-3.3.1-4-guacamole.zip" by twrp & reboot to recovery
-format data (yes), install "Disable_Dm-Verity_ForceEncrypt", install "magisk v20.1, reboot to system & finish android setup
-unlock developer options, reboot to recovery, install kali-nethunter "nethunter-oneplus7-oos-pie-kalifs-full-2019.4.zip" by twrp [or optional - builded .zip file], restart to system
-first startup of nethunter app, allow everything, restart to system
-[optional] update nethunter app from store, update metapackages, update kali, restart to system

*****************************9.5.8.GM21BA*********************************************
-install stock recovery guacamole msm tool "9.5.4.GM21BA" & finish android setup
-local upgrade with "9.5.8.GM21BA" & restart to system
-unlock developer options, unlock bootloader-here automatic wipe & finish android setup
-unlock developer options, reboot to bootloader, flash "twrp-installer-3.3.1-4-guacamole.img" by fastboot, reboot to recovery
-install "twrp-installer-3.3.1-4-guacamole.zip" by twrp & reboot to recovery
-format data (yes), install "Disable_Dm-Verity_ForceEncrypt", install "magisk v20.1, reboot to system & finish android setup
-unlock developer options, reboot to recovery, install kali-nethunter "nethunter-oneplus7-oos-pie-kalifs-full-2019.4.zip" by twrp [or optional - builded .zip file], restart to system
-first startup of nethunter app, allow everything, restart to system
-[optional] update nethunter app from store, update metapackages, update kali, restart to system

*****************************9.5.11.GM21BA*********************************************
-install stock recovery guacamole msm tool "9.5.4.GM21BA" & finish android setup
-local upgrade with "9.5.11.GM21BA" & restart to system
-unlock developer options, unlock bootloader-here automatic wipe & finish android setup
-unlock developer options, reboot to bootloader, flash "twrp-installer-3.3.1-4-guacamole.img" by fastboot, reboot to recovery
-install "twrp-installer-3.3.1-4-guacamole.zip" by twrp & reboot to recovery
-format data (yes), install "Disable_Dm-Verity_ForceEncrypt", install "magisk v20.1, reboot to system & finish android setup
-unlock developer options, reboot to recovery, install kali-nethunter "nethunter-oneplus7-oos-pie-kalifs-full-2019.4.zip" by twrp [or optional - builded .zip file], restart to system
-first startup of nethunter app, allow everything, restart to system
-[optional] update nethunter app from store, update metapackages, update kali, restart to system

*****************************10.0.GM21BA*********************************************
-install stock recovery guacamole msm tool "9.5.4.GM21BA" & finish android setup
-local upgrade with "10.0.GM21BA" & restart to system
-unlock developer options, unlock bootloader-here automatic wipe & finish android setup
-unlock developer options, reboot to bootloader, flash "twrp-3.3.1-74-guacamole-unified-Q-mauronofrio.img" by fastboot, reboot to recovery
-install "twrp-3.3.1-74-guacamole-unified-installer-mauronofrio.zip" by twrp & reboot to recovery
-format data (yes), install "Disable_Dm-Verity_ForceEncrypt", install "magisk v20.1, reboot to system & finish android setup
-unlock developer options, reboot to recovery, install kali-nethunter "nethunter-oneplus7-oos-ten-kalifs-full-2020.1-rc12.zip" by twrp [or optional - builded .zip file], restart to system
-first startup of nethunter app, allow everything, restart to system
-[optional] update nethunter app from store, update metapackages, update kali, restart to system

*****************************10.0.2.GM21BA*********************************************
-install stock recovery guacamole msm tool "9.5.4.GM21BA" & finish android setup
-local upgrade with "10.0.2.GM21BA" & restart to system
-unlock developer options, unlock bootloader-here automatic wipe & finish android setup
-unlock developer options, reboot to bootloader, flash "twrp-3.3.1-74-guacamole-unified-Q-mauronofrio.img" by fastboot, reboot to recovery
-install "twrp-3.3.1-74-guacamole-unified-installer-mauronofrio.zip" by twrp & reboot to recovery
-format data (yes), install "Disable_Dm-Verity_ForceEncrypt", install "magisk v20.1, reboot to system & finish android setup
-unlock developer options, reboot to recovery, install kali-nethunter "nethunter-oneplus7-oos-ten-kalifs-full-2020.1-rc12.zip" by twrp [or optional - builded .zip file], restart to system
-first startup of nethunter app, allow everything, restart to system
-[optional] update nethunter app from store, update metapackages, update kali, restart to system

Like I wrote, I would like to go little deeper in this, so I found the commit of Re4son - Add experimental USB gadget support to OP7 , also tried to uncomment init.nethunter.rc file,next I builded and installed directly from twrp skipping previous moves, on android9 there is black screen, on android10 there is some memory error.

Is it possible to get some documentation directed on porting HID interfaces with nethunter?

Propably actual init.nethunter.rc file is from other device? If yes, is it possbile to get more information?

That's true. I found also there should be hidg directory, that is what nethunter app want's.

In init.nethunter.rc file from devices/pie/oneplus7-oos/ramdisk or devices/ten/oneplus7-oos/ramdisk I found hid.0 and hid.1, nothing like hidg. This are my first founds, thats why I need some documentation.

I would like to help, with this stuff, I'm able to test your builds or to build it by my self.

P.S.

Found DriveDroid can make bootable USB and it works fine.