Onkyo (and thus Integra) did not release the firmware to the public - they wanted you to take your unit to an authorized dealer for firmware updates. That's how the Onkyo 885 and Integra 9.8 were, and I believe the 886 and 9.9 were the exact same way. There is a
thread at AVS where a member named gurkey provided access to the firmware files and instructions for installing them. The thread still seems to be active, so it's probably the best place to go.