I find myself reconfiguring my smartphone countless times; much more than my computer. Is there something that works like nix to define my config on a device, like apps, email, calendar accounts, etc.?
There is the Mobile NixOS project, but I don’t think it’s ready for daily use yet.
Is this what you are referring to? https://mobile.nixos.org/
It is, indeed.
All about NixOS - https://nixos.org/