I used to agree with your conclusion. But, experiment trumps theory. I discovered experimental evidence that it might be possible to communicate FTL. My paper in Medium is called An Experimental Demonstration of the Hypothesis That the Dirac Sea has no Speed Limit, and the experimental paper is “Quantum Holography with undetected light”, in “Science Advances”

https://www.science.org/doi/10.1126/sciadv.abl4301

To quote part of the abstract: “We implement phase-shifting holography with nonclassical states of light, where we exploit quantum interference between two-photon probability amplitudes in a nonlinear interferometer.” Nonclassical states of light are entangled photons. So, what this is saying is: We use phase shifting holography to measure the effects of entangled photons that encounter an object, on their entangled counterparts, and measure what the object encountered looked like with a digital camera.

The only way this could happen is if there was a connection between the entangled photons. This experiment did not prove that the connection was instantaneous, but I think it is and thus, shows the direction for new experiments to find out. All one needs to do is increase the length of the path of the photons interacting with the target so that the time of flight can be measured with sufficient accuracy.