Only 12c is supported per https://confluence.atlassian.com/adminjiraserver074/supported-platforms-881683157.html
Even if it works on 11, I would not risk it.
Also, PostgreSQL tends to have a lot more burn in than any other DB due to it's broad internal use at Atlassian. I recommend it to most of my clients, as long as they have staff who can support it (or they're equaly not qualified to support any of the supported DBs).
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