"Device information (i.e. the device that runs the application you use to access Plex): Advertising id, architecture, city, country, device, device id, display, latitude-truncated, longitude-truncated, memory, model, orientation, platform, platform version, power, region, screen resolution, timezone, vendor, watch connected, zip."
Plex collects an extensive range of device data including advertising ID, device ID, memory, power status, screen resolution, and truncated GPS coordinates, much of which goes beyond what's needed for core media playback functionality.