It was that I couldn’t pass it via the connection string with:
server = "couchbase://10.0.2.207:8091/pools?send_hello=false"
It took me a while to figure out that to get it to work I had to edit the radiusd.service systemd.
When looking at Unable to connect to server since client 2.7.3 thread, I was under the impression I could set the send_hello=false directly from there.
I hope that makes sense.