Allow markup inside drupal 8 Link function
Use the Markup class:     

use Drupal\Core\Link;
use Drupal\Core\Url;
use Drupal\Core\Render\Markup;

$url = Url::fromUri('http://www.example.com');     
$linkText = 'My link &lt;br&gt; containing tags';
$linkMarkup = Markup::create($linkText);
$link = Link::fromTextAndUrl($linkMarkup, $url);
$link = $link-&gt;toRenderable();