Signal is not the place for top secret communications, but it might be the right choice for you – a cybersecurity expert on what to look for in a secure messaging app

Signal is good, it's just that if you using a non-department approved phone the state intelligence Services of other countries, who are quite obviously interested in what the high level of government officials are doing and would put lots of resources typically to them, they might hack your phone. Signal was never designed with that particular use case in mind.