You can install your SSL certificate and modify the public endpoint in Dynatrace to accomplish that.
Changing the Web URL endpoint as in Alonso's post is required but all that this does in and of itself is change the URL that gets included in things like email alerts. Dynatrace can't manage any DNS outside of the .dynatrace-managed.com domains that are set by default.
So to use a custom URL you need to set up your own DNS configurations with the names you want and direct them to your cluster. As Alonso said you'll also need to manage the certs in this case for the same reason.