Are you sure the Samsung Galaxy S26 Ultra is safer than the Xiaomi 17 Ultra? Xiaomi doesn't display ads, and cryptocurrency wallets work perfectly fine on it. Any software wallet is unsafe, and for large cryptocurrency amounts, you should use a hardware cryptocurrency wallet in conjunction with it. If a user installs a lot of different software from external apps, they will have security issues on any Android phone.
I am not an iOS/iPhone user, but I have heard that, in terms of providing privacy, it is better than Android programs.
Other than this, I have not used hardware cryptocurrency wallets, but I am considering using them soon for the safety of my crypto assets.
Here, external apps, do you mean open-source applications, or those apps that are installed from the Google Play Store?
As usual, applications that are installed from the Google Play store are mostly considered safe, but those apps that are installed on a mobile phone using external links are unsafe in the majority of cases because they may contain loopholes that may attack your device and lead to high risk.