I Tried this several times. It never gave me the privacy 7 security warning though. I'm assuming since I've previously downloaded other third-party software.., but I Still don't see it in the menu. I don't know what I'm doing wrong.Ok... so I tried something a little different, and it worked.
On the GitHub download page for the plugin, i downloaded the pkg from the "assets" section.
It complained about being not secure - went to "security and privacy" panel in preferences, and clicked install anyway.
Restarted the computer - and NDI now appears as a source.