
Late January Puppeteer 2.1.0 got released, with native support for Firefox:
The launcher now has an option to run Puppeteer with different browsers, starting with Firefox. Puppeteer can now talk to a real, unpatched Firefox binary. This is a first step towards eventually deprecating the separate
puppeteer-firefoxpackage in favor of supporting Firefox directly in puppeteer itself.
You can define which browser to use by setting product on the options object to either "chrome" or "firefox", or by setting the PUPPETEER_PRODUCT env variable to one of those values.
puppeteer.launch({product: 'firefox'});
Installation still per NPM/Yarn
npm i puppeteer