Or is this impossible and we will always need dedicated hardware that is separate from devices like phones and computers for security reasons when it comes to large amounts of coin?
Even if there was something like that, why would you opt to use that instead of a standalone device that you only connect to when you need it to sign transactions and move your crypto? A phone that you use for all kinds of activities shouldn't be used as a storage for your private keys and seeds. Too many things could go wrong despite what the manufacturers say. Many people simply use their phones as a testing ground for games and dubious apps. They allow permissions and give apps rights without considering what it means. That's not an environment for your digital assets and their signing keys.
To discourage that kind of habit, it is best to remove the WiFi, Bluetooth, NFC and other components that can be used to connect to other devices and to the internet.
I doubt you will have much success trying that. Those components are surely all soldered to the main board, and unless you know what you are doing and have an engineering background, you are more than likely to destroy your phone. All the antennas and chips can be disabled on the software side, but who knows who and what can turn them on again if required to.
Passport started as ColdCard fork but with open source software and hardware, with added improvements and much better look.
I thought they were a fork of Trezor's codebase. Doesn't ColdCard work with a license that doesn't allow anyone to redistribute, use, or modify their code for their own purposes? Or maybe that wasn't the case when Passport forked it...