Mobile cannot connect to my local jitsi server

I install a environment in a lan refer to
I can start a call in my laptop,but cannot connect to the meeting using my andriod phone.

jitsi server url is

For mobile you need a trusted certificate, like Let’s Encrypt, which will not work with and ip address.

Thanks for you reply @damencho.

Certificate is difficult for me.
Who know the src code of andriod app downloaded from