Assuming that you'd like to redirect to some.xhtml which is placed in web root folder:
You can just continue using plain HTML.
<a href="#{request.contextPath}/some.xhtml">go to some page</a>
For conditional rendering, just wrap it in an <ui:fragment>.
Or use <h:link> with implicit navigation.
<h:link outcome="/some" value="go to some page" />
Note: no need to prepend context path nor to include FacesServlet mapping.
Or use <h:commandLink> with ?faces-redirect=true.
<h:commandLink action="/some?faces-redirect=true" value="go to some page" />
Note: no need to prepend context path nor to include FacesServlet mapping.
Or use <h:outputLink>, but you need to specify context path.
<h:outputLink value="#{request.contextPath}/some.xhtml" value="go to some page" />
Redirecting to an external URL is already answered in this duplicate: Redirect to external URL in JSF.