The HDMI OUT port is on the bottom of a vertical row of HDMI ports. It will require a bit of digging to get to it. It is also about a fifteen year old HDMI 1.3a specced unit. So, I’d just move onto a new unit supporting HDMI 2.0/2.1, HDCP 2.2/2.3, Dolby Atmos and DTS:X for the height speakers option as was mentioned.
The new HDMI and HDCP specs will be required for any new devices and TV in the system that support 4K and HDR. Even if repaired, the Pioneer will limit any connected devices to 1080p SDR.
If considering another used and/or refurbished unit, Accessories4Less has units available from Denon, Marantz, Onkyo, Pioneer and Yamaha. A few models come with three year warranties.