Amazon AppStream 2.0 adds support for 4K Ultra HD resolution on 2 monitors and 2K resolution on 4 monitors
Starting today, Amazon AppStream 2.0 supports 4K Ultra HD resolution on 2 monitors and 2K resolution on 4 monitors. For any AppStream 2.0 instance type, you can use up to four monitors, with a maximum display resolution of 2560×1440 per monitor. Graphics instance types support use of up to two 4K monitors. To use this feature, you must start your streaming session with the AppStream 2.0 Windows client. In addition, you must use an AppStream 2.0 image that uses a version of the AppStream 2.0 agent released on or after September 23, 2019.
Source:: Amazon AWS