People You Know
While you were doing your threat model, you likely realized that you are significantly more likely to have your digital privacy attacked by someone you know than a stranger. Whether they do it by accident by opening the wrong folders, on purpose by reading your messages, the likelihood of your data being compromised via non-technical means is significantly higher than anything else.
For many people, their greatest risk is their significant other or parents going through their devices, or worse, installing an app that allows remote access or tracking. Domestic violence enabled by technology is a very very real thing. There is a lot to say about this, but I'm not qualified, so I'll leave it to people like HackBlossom.
After bosses, friends, partners, and relatives, the next most likely risk comes from their devices being stolen (or seized) by a third party, who then go through the data. We'll go over the things you can do to make that less of a risk as well.