I am compiling from source and my install does not have chan_sip.so. I will find out if it is included in the deb packages.
You will need to see the manual reference for all of the modules you need to load for chan_pjsip.
I have confirmed that chan_sip is included in the deb package.
This old thread showed up as new in the UI and I just read it. All of the questions here should be answered in this post Flowroute Autopatch With Node Behind NAT Working