From my perspective, it kinda depends on what phone your friend has.
If they have an iPhone, and want to be able to integrate both systems, then macOS. If they're on Android, then Mint.
Prior to my shift to Linux, I was all in on Apple. My MacBook, iPad and iPhone all worked beautifully together. These days I have a Pixel running Graphene, and my computing is a mix of macOS and Kubuntu, and while I'm using Kubuntu my iPad is basically useless. KDE Connect is spotty at best, and while SyncThing theoretically works, it's too much of a faff to bother setting up. Oh, and Apple Music is essentially non-existent on Linux if you value lossless audio.
However, there are ways to integrate. Signal works well across the platforms for messaging, and even WhatsApp to some extent. Firefox is decent enough on iPad so you can sync tabs across. And WinBoat will run Apple Music in a VM, though that obviously takes a reasonable amount of utility from your computer.