Encrypt your files before upload them to OneDrive this way you use Microsoft servers and your files cannot be accessed by them to train AI and sell your personal data
Microsoft does not sell personal data. Do you have any idea how fast they'd get sued if there was any evidence of that?
You know who sells your personal data? Data brokers. But they don't have recognizable names or market their services to consumers, so they're less satisfying to complain about.
Feel free to assume everyone is trying to stab you in the back all the time. Sounds like a miserable way to live to me, even if it keeps you marginally safer.