Can't open filemanger to choose the boot.img

[gaohuadong]

install Magisk app and launch app, can't open the filemanger to choose the boot.img when I want to patch boot.img and click "Select and Patch a file". the platform has the filemanger (com.android.documentsui).
Does the app support Car platform?
I have the userdebug version android image, Can I user other method to patch boot.img or install magisk ?

Device: AOSP on Intel Platform
Android version: android 14 (Car platform)
Magisk version name: v28 or v27
Magisk version code: 28001 or 27000