On my Linux laptop, I use bubblewrap sandboxes with their own encrypted filesystems and granular permissions for each of my projects. Very easy and secure with NixOS, surely better than what I could do with an Android device.

This is something that no Linux phone enthusiast seems to understand.

Also if we use atomic distros with flatpaks and whatnot that mimic Android security the end user basically ends up having to essentially use Termux (but busybox or something similar) on their Linux phone as well

Stop repeating this nonsense, AOSP isn't any more "private" than Linux. AOSP is only more "secure" because, on some devices like Pixels, it exploits hardware features typically not found on general purpose computers. By default, Android also limits user control and takes root away. That may be a sensible design for an appliance, but it isn't something we should want on desktops.