Platform: mtk5862
System: android 9
Requirement: The native settings need to be deleted, but the non-native settings do not have the adb debug switch, making it impossible to use adb to debug the system.
Solution: After booting, enter setprop persist.sys.usb.config adb through the serial port, then enter getprop persist.sys.usb.config. After confirming that the obtained value is adb, enter reboot to restart the machine.
After the machine restarts, enter ifconfig through the serial port to check the IP address xxx.xxx.xxx.xxx of the connected device, and confirm whether it can be connected through the window command line adb connect xxx.xxx.xxx.xxx.