Does everything else in your house run open source firmware? How does source being available tell you whether your device is secure? Are you auditing it, then

Does everything else in your house run open source firmware? How does source being available tell you whether your device is secure? Are you auditing it, then building and installing the firmware yourself so you know that the binary matches the released source? Are you doing the same with the bootloader? How far are you willing to take your paranoia?