Is Jitsi using SRTP by default?

is Jitsi using SRTP by default ? I don’t see it in the SDP.

if not, how to enable it ?

They are off by default, you can configure them from the Security tab in the sip account settings, RTP/SAVP indication, off by default.

thanks. what’s the UI ?
is it a OS setting or Jitsi setting ?

This is Jitsi Desktop sip account settings.