Apparently it's not compatible. This was the response we got from Atlassian support:
Thank you for reaching out to Atlassian Support, and your research into the compatibility is correct.
Portfolio is not compatible with Jira 7.10.X at this point, there are a few conflict points with the newly introduced project archive features and the Performance improvements in 7.10 that change the ranking values that portfolio rely on for the calculations and scheduling algorithms. We are on schedule for an updated version of Portfolio compatible with these changes.
This is entirely contingent on our testing and QA but this should be ready to go by the end of next week, but at the moment 7.9.2 is the lates version of jira compatible with Portfolio, and the portfolio application will fail to load if you upgrade to 7.10 at this time.
Hello Community! We thoroughly enjoyed this just-for-fun conversation in the Jira Admin Group about what it's like to be a Jira Admin. For #JiraJuly, our talented designers created these graphics t...
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
You're one step closer to meeting fellow Atlassian users at your local event. Learn more about Community Events