Data plan required. 5G is available in select markets and through select carriers. Speeds vary based on site conditions and carrier. For details on 5G support, contact your carrier and see apple.com/iphone/cellular.
I have the same issue, my environment is Mac Mini running Sonoma 14.1.1 and Zoom Version: 5.16.6 (24664). At the moment to choose my iphone camera I can hear the connected sound chime but the screen is completely black... Any idea?