Errors getting started with joern

Not sure if a github issue is the right spot for this, but I couldn't find a place to ask about this.

I am trying to get cpg installed for the sole purpose of being able to extract, in csv format, all of the vertices and edges (with their labels/properties) of the cpg for c/c++ code (for the purpose of getting the graph, not to analyze the code itself). I could not determine a way to do this with just Joern, so I am trying to get the codepropertygraph installed and setup, because according to the understanding-cpg link on the documentation wesbite, it is possible to serialize the graph to CSV.

While that is a problem in itself (I have not found anywhere in the docs that mention how to serialize to csv), I am having problems getting started with this.
I have scala-build-tools and open-jdk8. (output of java -version is: openjdk version "1.8.0_222"
OpenJDK Runtime Environment (build 1.8.0_222-8u222-b10-1ubuntu1~18.04.1-b10)
OpenJDK 64-Bit Server VM (build 25.222-b10, mixed mode)"

I also installed protoc-3.9.1-linux-x86_64 from the releases page linked in this repo's readme, and added both the includes and the binary to /usr/local/include and /usr/local/bin respectively.

I then ran sbt publishM2, which had quite a few errors along the way. I saved the output to a logfile here:
publishM2.log

Any idea why I am running into troubles here?

Alternatively, if there is a different way of serializing an entire cpg using just joern (which I was able to successfully download and get running), any pointers on how to do that?

Thanks

Start with the repository README, the linked understanding-cpg documentation, and the attached publishM2.log; then review how Joern and codepropertygraph are expected to be used for CPG serialization. Done would mean documenting a supported setup path and the available way to serialize a complete CPG to CSV, or clarifying that this workflow is unsupported.