Solution was gracefully provided by @fatso83 in answer to my ticket: sinonjs/sinon#2155
The problem is with there being both global and window, due to JSDOM usage in this setup. Creating fake timers as:
const now = new Date();
const clock = sinon.useFakeTimers({ target: global, now });
solves the issue.
npm install
npm run serve
npm run build
npm run test:unit
npm run lint