This is posted relatively often, and every time it is posted I feel compelled to note that said dev has not articulated any real reason to consider Signal insecure beyond an implicit conspiracy theory with no real meat to it.
"Signal's use luckily never caught on by the general public of China (or the Hong Kong Administrative region), whose government prefers autonomy, rather than letting US tech control its communication platforms, as most of the rest of the world naively allows."
When you're holding up China as an example for the world to follow for privacy, I have a hard time taking ANYTHING else you're claiming seriously.