A good security is a trade-off: if you need to protect high values, you need to invest also higher efforst in security. You need to get away from trusting a mobile device, an operating system or the code to be secure just with their default installation. INVEST IN SECURITY!
Indeed, the problem is the HARDWARE itself is compromised, specially modern computers. Anything after 2008 is insanity tier levels of compromised hardware to use within Bitcoin stuff it seems. So basically, i3, i5, i7 computers as well as AMD have built in backdoors, exploits, at the hardware layer, this means that not even Gentoo Linux will save you, if you are using modern computers.
We are STUCK with old ass computers. It is unfortunate, but what can you do? The more advanced computers become, the bigger range of exploits, built-in-OS in constant communication with NSA and so on.
So to sum it up, if one wanted maximum security levels, you would need to use a pre-2008 computer, with Linux, a decent distro... that's about as good as it gets, still not perfect, but it's all we got, until we can get open source computers somehow.