Basically all source is open. Eyes are plenty. Somebody would raise a stink. People can also notice things while monitoring their network via a number of tools like Wireshark, etc. All it takes is one person to notice and share their findings.
replyIt also helps that "Linux" isn't a monolith. One person's installation can be very different from another in terms of the software used. If one piece of software collects, that collection isn't as valuable as Microsoft's because the userbase is much smaller.
It should be noted that the "correct" usage of /etc/machine-id is that you use it in a way that doesn't allow cross-correlation between different applications by using a HMAC of the machine-id with an application-specific UUID instead of using it directly. systemd-id128 has a command line flag to do this for you.
replyWhether everyone does that correctly, that's a different question. On the other hand, while developers should be more careful about how they use identifiers like this, if an application on your machine wants to track you they don't need /etc/machine-id.
Yes I think privacy and security on the desktop has fallen way behind mobile and we need much stronger protection these days.
replyMobile's came at the cost of composability between programs and the imposition of policy, which are against the Unix Philosophy. I wouldn't make that trade. Mobile's a sad state of affairs, inferior to desktop in many ways.
replyYou can most likely get better security than mobile's, you just need to e.g. learn to write your own SELinux policies, etc.