V13.x Have tried using Html.ActionLink and Url.Action on a couple of V13 sites as tests and each time the href attribute is empty. The code is showing that the methods and controllers are resolved but nothing come out on the html. It's just My Text. Is this Umbraco interfering somehow? Is it possible to get it to work? If not, what are the workarounds? Thanks.

you could try this

<a asp-controller="testsurface" asp-action="index">test</a>

I just hard coded it in the end. Simple 😉