How to enable USB Serial debugging on Lumia 950 XL running Linux

[Clrs17]

I'm currently porting OpenHarmony ( a Linux distro which have some similarity to Android) to Lumia 950 xl device and the kernel has successfully booted up. However, to conduct further debugs, it's necessary to access the shell to test the rendering and boot up the desktop environment. The problem is we failed to connect to it using USB serial, even if we set the kernel compile config. So, how to do that or are there alternative ways to access the shell? Thanks a lot!