I think op is trying to say secure wallet among the mobile wallet not comparing with any other wallet like paper wallet, hardware wallet or something like that. But there are a lot of mobile wallet and Op is trying to say that trust wallet is the secure wallet among the mobile wallets.
Mobile wallet for bitcoin, I can still suggest Electrum or Bluewallet. That supports few altcoins and tokens, I will go for Mycelium. But for users that want more altcoins, the best is to just get an hardware wallet which is open source.
In the OP, it was mentioned that Trustwallet is open source, that is not true, the reason not to use Trustwallet, the reason it is not secure, nothing about the wallet is known to the public concerning its source code. Using a wallet which you do not know if having a spyware or other malware, is that secure?