The point is, you wouldn't know unless you have complete understanding on every aspect of your device and every bit of the software.

Nobody would be installing a Linux kernel and use the phone like that, they would be installing a distro. There are so many vectors of attack, the person who puts the distro together doesn't need to have malicious intent, the supply chain could be compromised.

Probably not intentionally, but there are likely a bunch of 0-day exploits we don’t know about.

You know, it's getting so big and warty that I'd be surprised if it wasn't.