The current best practice is to create or edit the glide.entry.first.page.script System Property that needs to have the value of new SPEntryPage().getFirstPageURL()

The recent SPEntryPage script includes code will redirect the end user to the portal (sp_portal) that has default=True, so you need to make sure that ONLY the ESC portal has the deault=true

as reference:

https://docs.servicenow.com/bundle/washingtondc-platform-user-interface/page/build/service-portal/co...

https://docs.servicenow.com/bundle/washingtondc-platform-security/page/administer/login/task/t_Speci...