In my school days I was able to add FLAC support to an iPod Touch 4th gen with a quick Cydia module(?) download. I'm skeptical of your claim that macOS doesn't support FLAC. I'm sure mpv and other programs can play it fine. Do you just mean support in the default-installed macOS software? That seems like pretty limiting criteria. I wouldn't expect something like Windows Media Player to cover all that much either.