This starting failing since we updated from v2.1.0 to v3.1.0 of Puppeteer in Bug 1632710

itFailsFirefox('should press the meta key', async () => {
    const { page, isFirefox } = getTestState();

    await page.evaluate(() => {
      window.result = null;
      document.addEventListener('keydown', (event) => {
        window.result = [event.key, event.code, event.metaKey];
      });
    });
    await page.keyboard.press('Meta');
    const [key, code, metaKey] = await page.evaluate('result');
    if (isFirefox && os.platform() !== 'darwin') expect(key).toBe('OS');
    else expect(key).toBe('Meta');

    if (isFirefox) expect(code).toBe('OSLeft');
    else expect(code).toBe('MetaLeft');

    if (isFirefox && os.platform() !== 'darwin') expect(metaKey).toBe(false);
    else expect(metaKey).toBe(true);
  });

I don't think it makes sense to spend time on that regression anymore for CDP. Now that Puppeteer is transitioning over to WebDriver BiDi we can make sure that meta key handling is properly supported.