It is difficult, you should not hold any significant amount of money on your phone in any case.
Anyone with large amounts of bitcoin in self-custody should be using the passphrase feature IMO,
so they can't steal your bitcoin with just the seedphrase alone. It is your last line of defense.
It's not about using passphrase or any other extra security including multi sig, once you installed the fake apps, they can gain access into your smartphone.
The most important thing is hold large amount of coins in hardware wallet or air-gapped wallet, not in hot wallet. Also don't save every password or any secret information in your smartphone.
This guy understands it. Even if you don't install a fake wallet, there is often many malware applications on both stores. It can be even a simple mobile game. If you install it it can steal your wallets even if you have a real wallet.