Okay, some investigations shows, that my Jitsi client sends data to the wrong IP. Server have few, for example 18.104.22.168 and 22.214.171.124. My computer is in the 126.96.36.199 network only, and the account is myname@domainname. The domainname is in HOSTS, but Jitsi does not use hosts. So, I wrote 188.8.131.52 in the "override" section in preferences.
Now, why on Earth it sends UDP traffic to 184.108.40.206 ???