Is there an equivalent to Html.Raw in Blazor?

Yes, sample:

@page "/"

<h2>Title</h2>
<hr />
<p>
    @ms
</p>

@code {
    MarkupString ms => (MarkupString)description;

    string description = $@"
This is an example of how Azure serverless functions can be consumed from Blazor WASM.
<br><br>
To run this project in development mode, the <b>HttpTriggerSample</b> project must be run simultaneously.
<br><br>
Serverless Functions origin: <b>{fs}<b>.";

    // by example
    static string fs => Program.IS_DEVELOPMENT ? "DevelopmentStorage" : "Azure";
}

Feature to render raw HTML was added in Blazor 0.5.0 version. This is the example of how raw HTML can be rendered from string containing HTML content:

@((MarkupString)myMarkup)

@functions {
    string myMarkup = "<p class='markup'>This is a <em>markup string</em>.</p>";
}

More info can be found in "Blazor 0.5.0 experimental release now available" announcement.

Not right now, but will have it probably in the next version: Follow this.

Workaround (from that issue):

cshtml

<pre>
    <span ref="Span"></span>

    @functions{
        [Parameter] string Content { get; set; }
        private ElementRef Span;

        protected override void OnAfterRender()
        {
            Microsoft.AspNetCore.Blazor.Browser.Interop.RegisteredFunction.Invoke<bool>("RawHtml", Span, Content);
        }
    }
</pre>

index.html

<pre>
    <script>
        Blazor.registerFunction('RawHtml', function (element, value) {
            element.innerHTML = value;
            for (var i = element.childNodes.length - 1; i >= 0; i--) {
                var childNode = element.childNodes[i];
                element.parentNode.insertBefore(childNode, element);
            }
            element.parentNode.removeChild(element);
            return true;
        });
    </script>
</pre>