You're still going to have a very hard time convincing the jury that Signal booby trapped your phone to download child porn at random from the dark web.
Law enforcement doesn't confiscate and use Cellebrite on phones at random. If they have a warrant to search your phone, they already have some reason for suspicion.
For example, maybe someone accused the defendant of molesting a child, but the police didn't have hard evidence. They use Cellebrite and find some child porn. The defense argues that Signal might have planted it there with a booby trapped file that downloads stuff at random from the dark web. Do you think the jury will buy that?
At that point, why not just say you left your phone unlocked in public and a stranger probably used it to download the child porn?
Law enforcement doesn't confiscate and use Cellebrite on phones at random. If they have a warrant to search your phone, they already have some reason for suspicion.
For example, maybe someone accused the defendant of molesting a child, but the police didn't have hard evidence. They use Cellebrite and find some child porn. The defense argues that Signal might have planted it there with a booby trapped file that downloads stuff at random from the dark web. Do you think the jury will buy that?
At that point, why not just say you left your phone unlocked in public and a stranger probably used it to download the child porn?