Given the fact that Signal is E2EE, “full access” would mean “full access to encrypted data without the keys to unencrypt it,” which is why E2EE is important in the first place. Were Signal compromised, US representatives would not resurrect the EARN IT Act year after year in an attempt to make E2EE illegal.

No one had provided a shred of evidence that Signal has been compromised. And given that they’re more willing to pull out of a country entirely v. compromising user data, I’d call them a pretty safe bet.

Of course, using add-ons also requires diligence, as each add-on from each source requires one to both trust the source and vet each source regularly. An add-on is also as trustworthy as the people that made it, and one must be willing to do the work the verify that those add-ons continue to be safe.