I mean, exactly how invasive are default operating systems? (Like Windows, Mac, Chrome OS, Android, iOS) Do they log your keystrokes, log passwords, capture screen, upload your photos, videos, or audio? (Assuming you aren’t a target of government) Is it even possible for the average person who doesn’t feel comfortable messing with installing operating systems to have any privacy?
It depends on what you consider spying. The vast majority of devices want some form of push notification capability, which requires being connected to Microsoft/Google/Apple servers, and thus the company knows your IP address. But doing pretty much anything on the internet and you expose your IP address.
If what you mean by spying you think it is looking at what app/program you are doing, recording your keystrokes, recording what your camera sees, the vast majority of devices don’t do any of this. Those are done on hacked laptops and school laptop admins that are either creepy and unchecked or overly intrusive.
Somewhere between these two extremes you would say it crosses the boundary into spying. You don’t need a custom OS to stop it unless you your threshold is all the way to the push notification level.