How do I keep on the same page by clicking on internal anchor links, using Aurelia?

You can disable the Aurelia router highjacking the link in several different ways, as per the documentation. One of the ways is to use one of these special attributes:

<a href="/some/link" download>Skip Hijacking</a>
<a href="/some/link" download="">Skip Hijacking</a>
<a href="/some/link" router-ignore>Skip Hijacking</a>
<a href="/some/link" router-ignore="">Skip Hijacking</a>
<a href="/some/link" data-router-ignore>Skip Hijacking</a>
<a href="/some/link" data-router-ignore="">Skip Hijacking</a>