As described in the public information below, currently asterisk (*) wildcard character is necessary to perform partial match search in the search function of the Portal add-on.
It would be great if the function which allows partial match search without using the asterisk (*) will be implemented as a default search function.

Title : Add a webpage to render a list of records
URL : https://docs.microsoft.com/en-us/dynamics365/customer-engagement/portals/add-webpage-render-list-records