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The Html style does not support <pre>
based on my test .
I even tried to use HtmlLabelPlugin , but still no luck , same result .
If you want to display the html perfectly , I suggest you use WebView .
Code
var browser = new WebView();
var htmlSource = new HtmlWebViewSource();
htmlSource.Html = @"<html><body>
<pre>Hello user<BR/>How are you</pre>
</body></html>";
browser.Source = htmlSource;
Content = browser;
Result
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