That's interesting that the OEM unit plays FLAC. That must be something recent, my 2018 will only play MP3. I'm sure it plays apple shit too, but who cares about that.
I don't really count replacement units, cars are getting to the point where you can't replace the OEM head.
The Mazda owners manual doesn't mention it, but it's there. It's actually sent me down a rabbit hole on how to format a 256gb thumbdrive in FAT32, technically possible under FAT32 specifications, but windows hasn't allowed it, moving on to try it with Linux next.
This utility for Windows is one I keep in my toolbox:
http://ridgecrop.co.uk/index.htm?guiformat.htm
It's called fat32format, and it does just that - formats anything to FAT32. I seem to remember FAT32 giving out about 200GB, so ymmv.
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