Signal is safe enough depending on your threat model

If you worry about aws centralization and outages then signal isn't a good option

If your worried about sgx enclave exploitation then it's not a good match

If your worried about us intelligence monitoring traffic then it's not a good fit

So signal is fine for person to person western traffic

Not a good fit for a country needing isolated highly secure messaging... I.e. the french government should NOT use signal, centralized in America, sgx exploits are a concern, and exposing the social and communication graph to the us intelligence services isn't in the french national interest