You could use javascript to check what browser the user has, then apply a CSS class accordingly... something like this
  const browser = (function (agent) {
    switch (true) {
      case agent.indexOf("edge") > -1: return "edge";
      case agent.indexOf("edg") > -1: return "chromium based edge (dev or canary)";
      case agent.indexOf("chrome") > -1 && !!window.chrome: return "chrome";
      case agent.indexOf("trident") > -1: return "ie";
      case agent.indexOf("firefox") > -1: return "firefox";
      case agent.indexOf("safari") > -1: return "safari";
      default: return "other";
    }
  })(window.navigator.userAgent.toLowerCase());
  if (browser = 'chromium based edge (dev or canary)') {
    const el = document.getElementById('#yourelement');
    el.classList.add('chromium');
  }
For reference the userAgent for chromium based edge looks like this 
mozilla/5.0 (windows nt 10.0; win64; x64) applewebkit/537.36 (khtml,
like gecko) chrome/76.0.3800.0 safari/537.36 edg/76.0.167.1
so you can see that includes the keyword edg
but there are no CSS rules that directly apply to chromium based edge - so using javascript is your only option