For Postman configuration, it’s completely fresh as newly downloaded, no extra configuration was made (I only use system proxy, but either turn on or off doesn’t affect this).
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I am not sure if my findings were correct, I think this is what the Postman team has been doing: GitHub - postmanlabs/grpc-node: gRPC for Node.js
Just did some check with the Functional framework MochaJS, they did have to also enable this option as:
const client = new proto.MyService(myTargetHost, channel, {
'grpc.default_authority': myTargetHost + '/subgrpc'
})