I daily drive secureblue; or, to be more precise, its bluefin-main-userns-hardened image.
“Why?”, you ask. Because security is my number one priority.
I dismiss other often mentioned hardened systems for the following reasons:
Qubes OS; my laptop doesn’t satisfy its hardware requirements. Otherwise, this would have been my daily driver.
Kicksecure; primary reason would be how it’s dependent on backports for security updates.
Tails; while excellent for protection against forensics, its security model is far from impressive otherwise. It’s not really meant as a daily driver for general use anyways.
Spectrum OS; heavily inspired by Qubes OS and NixOS, which is a big W. Unfortunately, it’s not ready yet.