Explanation for newbies: The GNU/Linux copypasta is an argument made by Richard Stallman that the operating system should be referred to as “GNU/Linux” or “GNU+Linux” because linux is just the kernel and what makes it useful are the various GNU programs and libraries like coreutils and glibc.
Alpine Linux is a linux distribution that ships without any GNU software (though it can be installed using the package manager).
I was going to say you have to start use Alpine with the Pine email client. But IIRC, Pine stopped development, and a new project called Alpine took over.
So, now use Alpine to run Alpine and start calling it Alpine Linux Alpine Linux.