Android jitsi meet does not work with dockerized jitsi backends

I’m the new guy to build up Jitsi and try it.
I started Jitsi backend commponent from this guide
It’s ok with LAN web access, but android app does not work.
My cert is self signed.
By the way : if i want to obtain Cert using letsencrypt, so i have to put system in a live DNS enabled server ?
Many thanks!