You stated it yourself, teams is a function within Jira Portfolio and not a native function so you can not get that functionality without any plugin.
There are other possible plugins that do similar things though if you think the cost of portfolio is to high. This free plugin might be something for you: https://marketplace.atlassian.com/apps/1220446/spectrum-teams
Welcome to Cloud Cafe – our video series about cloud app development on Atlassian. ✨ Ever heard the term Atlassian ecosystem and wondered just exactly what it meant? Grab a cup of ☕ and join ...
Connect with like-minded Atlassian users at free events near you!Find an event
Connect with like-minded Atlassian users at free events near you!
Unfortunately there are no Community Events near you at the moment.Host an event