Finally I've managed to do that without any 3rd party addons. The key is to get
boot.img, and modify the file
default.prop that is living in the root folder inside the
You have to do three modifications:
You can get the
boot.img if you extract the flash image with the OS you are currently using, or by extracting it from the device directly.
After that, the
adb logcat will collect the live boot messages when you connect your laptop to the phone when it boots.
With adb secure on '1', it will give you 'unauthorized' message when you attempt to adb.
ro.secure=0 allows adb to have root privileges (see more here https://android.googlesource.com/platform/system/core/+/master/adb/daemon/main.cpp)
All credits go to the IRC users LuK1337 and razorloves from the LineageOS Discord/IRC channel.