Oh, if you're using homebrew and you want ffmpeg to support ALAC, you can do that. brew edit ffmpeg; add `depends_on "fdk-aac"` and `--enable-libfdk-aac`, `--enable-nonfree` to the relevant sections, remove the bottle section; then, brew reinstall ffmpeg. There's probably a better way to do this that doesn't trigger a merge conflict each time they update the bottle hashes (resolved easily with brew edit ffmpeg, repeat above), but I'm lazy and ffmpeg doesn't update frequently. I have no idea if ffmpeg can maintain ID3 tags from FLAC->ALAC or not, but if you have need of this knowledge someday, say hi to that future for me!

(And if compilation fails with a specific weird error about corefoundation corevideo coreaudio etc, uninstall and reinstall your macOS command line tools, because they're broken; `sudo rm -rf /Library/Developer/CommandLineTools ; xcode-select --install` will do that.)