A stock firmware (If you want restore your Android TV)
Method to root
Install latest Magisk Manager (now is 22.1)
Copy file magisk_patched-22100_XSRyq.img to your usb
Plug your USB at port 2 (near CARD)
Plug A-to-A cable to your computer
Open Command Prompt
Run command adb shell then run su
After that inject patched-boot with command dd if=/sdcard/magisk_patched-22100_XSRyq.img of=/dev/block/by-name/boot
Run adb reboot and now, your android TV is rooted with Magisk
Notes: With Android 10 you can not modify the system partition (It's read-only)
Method to restore stock firmware
Install Driver Assisstant
Open PhoenixSuite v1.10, switch to Firmware Tab and select img firmware.
Open Device Manager
Turn off your AndroidTV
Find a small stick and inject to AV port (It have a hidden button)
Press and hold that hidden button and plug your cable into USB (port 1). Note (You must hold the hidden button when plug USB cable into android box and pc)
Now you will see the Unknown device or something with warning labelin Device manager (At this step, you can free your hand)
Right click with warning label driver -> select Update Driver
Continue choose -> Browse my computer for drivers -> Browse -> Navigate to PhoenixSuite folder and select Drivers\AW_Driver.
Then update the drivers.
Now you can restore/upgrade/flash your android TV with the firmware