I really don't see how improving security and reducing privacy are related: like generating fingerprints of installed programs, or scanning the memory, disks for malware and reporting results to the OS provider/device manufacturer and mapping the results to a user account or an ip address ?
For me improved security was more synonym to degraded performance.
Hard to do I think. Even plain old "linux but for phones" is pretty difficult at this point because:
--most drivers and hardware specifications are proprietary, and probably secret under NDA
--most bootloaders are cryptographically locked and controlled by vendor
--necessary wifi and cellular modem hardware is the same, and are also patent minefields even in the foundational platonic ideals of design, as is mobile graphics hardware
--the modems are subject to regulatory requirements that they be secured from modification by the user/owner of the device
Secure in this context means secure from the user and device owner, which can arguably be for good reason -- think of an ATM kiosk, for example.
So no "tails for phones" yet, but people are trying. Check out postmarketOS, lineageOS, replicant, sailfish. Last I tried things were still kind of science project, like 90's style linux.
Adding ubports to the list- I have it on my Pinephone and can place and receive calls, send and receive SMS, and utilize GPS. There are some features that don't yet work on Pinephone like MMS but it's on the threshold of being daily-driver worthy.
Users on Pine64.org have reported their devices can run 14 hours on idle and my own experience is the battery will last all day with moderate usage. Getting it on the phone is as simple as getting Raspbian on a Raspberry Pi, you just flash the image onto an SD card.
I feel as though the improvements in security lend themselves to improvements in privacy, and vice versa, in a rather linear relationship.
That being said, privacy factors are primarily user-choice in that it is the optional apps and programs that compromise privacy, even if the privacy breaches are less-than-voluntary, as seen in the recent clipboard skimming scandal. Making an OS more secure by limiting unauthorized access to information like the clipboard is both more secure and more private.
For me improved security was more synonym to degraded performance.