Interesting this one. According to the user manual my 2018 Sport Navi will not play flac files.
As I have nearly all my music collection in the lossless flac format , I started converting some to mp3 and transferred to a usb stick solely for the car.
I inadvertently copied over some flacs without conversion only to find they play no problem !
Obviously the better sound quality is not appreciated in the car but at least it saves the hassle of conversion.