Even State Department-funded Human Rights Watch admits that authorities combine legal and illegal methods to obtain convictions: https://text.hrw.org/report/2018/01/09/dark-side/secret-origins-evidence-us-criminal-cases
Combining dragnet surveillance with device hacking is intended in the design of both tools. Hence, State Department-funded Signal dupes you into handing over your identity as part of the population-centric mapping. In custody, your phone will be hacked when it is taken away if it’s important.
https://xcancel.com/hannahcrileyy/status/2034273723667161480#m
At that point you can rely on nothing but Tor or I2P
Nothing else hides metadata better than Signal, without involving large networks of independent nodes that participate in Sybil resistant routing. The only thing that gets close is threshold schemes where you still need multiple independent entities running servers.