(How) Is it possible to add text-links to a report?
In this case of altering an existing template - find the function that controls how the activities are displayed and setting the $viewLinks variable to True - as shown below.

public function alterDisplay(&amp;$rows) {
    $entryFound = FALSE;
    $activityType = CRM_Core_PseudoConstant::activityType(TRUE, TRUE, FALSE, 'label', TRUE);
    $activityStatus = CRM_Core_PseudoConstant::activityStatus();
    $viewLinks = TRUE;
    $context = CRM_Utils_Request::retrieve('context', 'String', $this, FALSE, 'report');
    $actUrl = '';