lcalamar I can very easily manage the depth of security and privacy
Privacy, it depends but it is possible.
As for security, there is no public desktop OS (that I'm aware of) that comes even near to smartphone OS security, and no amount of hardening can achieve it. Ideally, a large team of skilled workers could rewrite the now-archaic desktop systems and create something new, but with open source developers and limited resources, that's quite unlikely.
So the best bet is likely to take an existing, open source OS and harden it, similar to how GrapheneOS does with AOSP; yes, the Linux kernel which has an immense attack surface is still in use, but the goal is to do that which is realistically achievable and useful for the average user.
Now as far as I'm aware, the desktop OS most closely aligned with security in mind appears to be ChromeOS (or ChromiumOS which is its open source variant). It is far from perfect and unlike most OSes, it's more oriented towards web apps than actual app software. But from a security standpoint and based on my understanding, this is the closest thing we have, followed by MacOS.