It might take me a few days to find the time to get an install of Lubuntu 18.04.1 with kernel 4.18.0-16 up and going to test this for you. That would at least get me in the ballpark of approximating your install. You could try installing the libelf-dev package that the error in the make.log is stating is missing and could be causing this issue.
The line in the make.log I'm referring to is:
Makefile:970: Cannot use CONFIG_STACK_VALIDATION=y, please install libelf-dev, libelf-devel or elfutils-libelf-devel
so try: sudo apt-get install libelf-dev (that should be the one that is relevant to your Lubuntu install).
Not knowing the state of your install (what iso/installer you used, what options you selected when installing, etc...) makes this a bit trickier to troubleshoot, but I'm sure we can figure it out.