Is it possible to have existing knowledge base articles pop-up before someone submits a ticket on that topic?

If you signed up before Aug 9, 2021, please click Previous plans to view your applicable plans.

Once you have populated your knowledge base articles, you can setup your support portal to "auto-suggest" solutions that are in line with a customers' query(Ticket Subject) when they are submitting a ticket.

If you navigate to Admin > Channels > Portal --> Settings tab, you would see an option called "Auto-suggest solutions while creating a new ticket", available under "User Permissions for portal" --> Who can submit a new ticket on portal.

You could turn this option on and each time when the customer starts submitting a ticket, based on the text added to the Subject, corresponding Solution Articles would be auto-suggested.