What you’re describing sounds very marketable, but—and this is me being a picky bastard, as per usual—I’d describe it more as “Internet privacy consultancy”. You sound like you’re wanting to offer a full-service, end-to-end privacy consultancy to customers, including advice. In that case, you have a very large base to cover: identifying and avoiding email attachment based threats, phishing threats, the same for social engineering attacks, using anti-virus, and so on.
Given that smartphones offer a different attack vector with potentially similar or better results for a bad actor, you should consider that avenue also.
I’m still of the opinion that Linux on the desktop as a mainstream computing option for “normal” users is a lost cause (cf Has the Linux Desktop missed its chance?).
In my mind, the best out-the-box option for a computer with strong privacy is a Mac. Apple are one of the few remaining heavily-privacy-focused computer companies out there. Safari is a very good browser with anti-tracking and anti-commercial features. On-disk encryption (another important privacy option which can be scary to implement on a Linux desktop-class system) is provided as standard. Backups are very, very easy to perform (plug in an external device or use a compatible local network storage device, boom, done).