I made a hint of progress, but now I'm well and truly stuck trying to get the Atom package to work!
Specifically, I had named my test file sonarlinter-test.js, when I renamed it to sonarlinter-triggers.js, the VS Code problems panel lit up with sonarlint errors and warnings -which would rock if VS Code was my day-to-day editor, but it isn't.
The one good and bad thing from this is that I'm getting sonarlint feedback from test file in both the CLI and VS Code.
Unfortunately, I'm still not getting any sonarlint feedback in Atom, neither the expected sonarlint warnings and errors nor feedback that would indicate configuration errors!
I've completely uninstalled the sonarlint package in Atom, reinstalled it, and worked my way through the different JDK/JRE configs (quitting & restarting Atom after each change) - all to no avail.
Does anyone have any suggestions on how I can get more information, suggestions on troubleshooting, things I should check/verify, etc so that I can get sonarlint working in atom?