Because WebExtensions still doesn't have a TCP sockets API, nor a spec, OverbiteNX uses its bespoke Onyx native component to do network operations. Onyx is written in open-source portable C with no dependencies and is available in pre-built binaries for macOS 10.12+ and Windows (or get the repo and build it yourself on almost any POSIX system).
To try OverbiteNX, install Onyx from the links above, and then install the extension from Mozilla Add-ons. If you use(d) OverbiteWX, which is the proxy-based strict WebExtensions add-on, please disable it as it may conflict. Copious debugging output is emitted to the browser console for this test version. If you file an issue (or better still a pull request) on Github, please include the output so that we can see the execution trace.