That's not true. I mentioned I'm currently using a Sony XBR-55X900F LED and a Sony XBR-65A9G OLED and Dolby Vision looks great on both sets. Your XBR900F is a full array LED. It has 4 HDMI 2.0b inputs and all are HDCP 2.2. To view the highest quality 4K and HDR content from connected sources, use the TV's HDMI 2 or 3 inputs. Have you tried adjusting your picture settings? Is your TV's software current? The current software version for the XBR900F is PKG6.7140.0358NAA.