The closest thing to secure, actually usable Linux distro on phones is Android; if you are serious about security and degoogling GrapheneOS especially. The bad thing is that you have to have a Pixel for that.
Source: I own a Pinephone and has tried both Phosh-based and KDE-based offerings, there is also Sailfish though. Out of these Sailfish is the only one close to usable as of now.
Source: I own a Pinephone and has tried both Phosh-based and KDE-based offerings, there is also Sailfish though. Out of these Sailfish is the only one close to usable as of now.