I’m not sure where you read that unsecured wifi is not supported. That’s not true. If you try to connect to an unsecured wifi and leave the password field blank, you will get this screen:
If you click “No Password”, the camera will go ahead and connect to the unsecured network. I’d be a little concerned, though, about the camera getting hacked in that environment.
HOWEVER, there are two reasons you may be having trouble:
Your open network is 5GHz only. WyzeCam requires a 2.4GHz network and will not connect to a 5GHz only network.
Your open wifi has a landing page. In other words, when you connect to the network with your phone or computer, a screen comes up where you have to click a button to accept terms and conditions, or something similar. If so, the WyzeCam will not be able to get past this page. Landing pages are common with public wifi such as hotels and airports.
The workaround for #2 is to use a travel router to serve as a bridge between the public wifi and camera. Once you connect to the public wifi through the travel router with your phone or computer (dealing with the landing page), then the camera will not need to deal with the landing page for its connection. You would need a travel router that supports WISP protocol such as the one linked below. One advantage of this approach is that it essentially adds VPN-like security to the open wifi setup.
GL.iNet GL-MT300N-V2 Mini Travel Router