Did you check if the /vendor partition is mounted correctly? Also, you probably need to change a symlink to get it into the right place. Plz join Telegram porting group, the forum i s not a good place to help you.
So disabling lightdm is the right thing for the moment, but please try first to debug the Android container before you try anything else on UT side. In your case, we need a logcat, try LD_LIBRARY_PATH=/system/lib64:/vendor/lib64 /system/bin/logcat and then also EGL_PLATFORM=hwcomposer test_hwcomposer should run without a crash first