If the device can access external Internet, you can call the Yealink Demo room for testing.
IP addresses are as below:
Yealink Demo1 117.28.251.50
Yealink Demo2 117.28.251.51
Yealink Demo3 117.28.251.56
If not, you can download Yealink VC Desktop with below link, then install on your PC for test.(They should be in same LAN):