However, you may need to use the NEW MOBILE APP instead of the Classic Mobile App. Since there are no examples for the new mobile app, you may wonder what the syntax on the payloads for the Push Notification Message Content is.
The answer is that in new mobile apps we no longer support directly passing web url in push notification payload.
To redirect user to a web page from push notification, it is now needed to configure a URL screen applet with the portal page url, then pass the sys_id of the applet in the push notification payload.
Information about configure URL Screen applet in Mobile Studio can be found in the Configure a URL screen documentation.
Information about setup push notification in new mobile apps can be found in the Set up Push Notifications in the New Mobile App documentation.
Worth mentioning is that currently ServiceNow only supports static URL for the URL screen applet. Should it be needed to configure a parameterised url there are currently no solutions.