Here's how to downgrade Shield TV to Android 9 after Android 11 update
SHIELD Software & Firmware Upgrade V9.1 | NVIDIA
NVIDIA Shield Will Update All Models To Android 11 | Digital Trends
Amazon.com: NVIDIA SHIELD Android TV Pro Streaming Media Player; 4K HDR movies, live sports, Dolby Vision-Atmos, AI-enhanced upscaling, GeForce NOW cloud gaming, Google Assistant Built-In, Works with Alexa : Everything Else