This error occurs when the action argument is 'null'or 'undefined' in /libs/granite/ui/components/coral/foundation/clientlibs/foundation/js/preference/preference.js. The value for action attribute is /home/users/<pathtousernode>/preference for POST call. This value is retrieved from the granite page meta element. Something like below,
<meta name="user.preferences" content="{"granite.shell.showonboarding620":"true","cq.authoring.editor.page.showOnboarding62":"false"}" data-foundation-preference-action="/home/users/h/h4hprefRyD2csCQg82s6/preferences">
The reason for this would be either the section of code computing this preferences meta element is overlayed or modified in your earlier versions of AEM and is getting impacted in upgrade. Please check the following code whether its overlayed or touched in your code and ensure you don't do that unless required as per AEM best practices.
/libs/granite/ui/components/shell/collectionpage/collectionpage.jsp
The following property in preferences node to be false for the pop-up to not appear again for the user.
granite.shell.showonboarding620 false.
Also validate its not getting overwritten during some LDAP sync or SAML login.