I am only a basic user of iPhones and that is the reason I keep an eye on this forum. I know how some stuff works and other stuff just defeats me. One of the things with the iPhone that defeats me is that when I wanted to try and turn off the annoying Siri, I used the iPhone search facility. The result was the setting I quoted previously. (“always listen for Siri“ in settings > accessibility > Siri). It would appear that things aren't always that simple.
My personal opinion of Siri is that it isn't useful for me and I just want it to leave me alone and stop just spurting out things like "I didn't understand that request", or something similar, when I haven't asked it for anything.