The Mac OS patch I recreated from @SherLynn description and indication did not have any unexpected behaviour. @SherLynn would need to provide the file.
@woland and the others: IT WAS A NETWORK PROBLEM! (not Hackintosh related)
I'm a bad network setter, I know it, but I thaught this time I learned my lesson... so I created a sub-network 255.255.255.255... meaning I was closing all gates!
A friend explained why the receiver could anyway see the other mac but I don't get it.
after that I did a 255.255.0.0 sub-network and it worked fine.
For network alergics like me, I put a print screen (sorry in french)
IP Adress1: 188.8.131.52 , IP Adress2: 184.108.40.206
After that I was able to have two good NDI feed (both sides) and a OSC transmit.
Thanks for your help,
redirecting a IzzyMap(ed) stage from the standard projector to a virtual stage channel?
It's on the road map.