My stereo still uses CD's, so that's what I use. I have a DVD burner in my PC, and a spindle of blank CD-R's and anothet of blank DVD-R's. I use the former to burn music CD's for my stereo, and the latter for extra backup whenever I'm about to upgrade my hardware (once every 10 eyars or so). This is on addition to a NAS and an external drive. I just figured that the disks would have the best chance to be read once I get a new desktop.
(I also saw the mention of floppies in the discussion. I have an old Win98 machine - for gaming only these days - with an internal floppy and zip drives. Those media easily outlast CD's: I can still read almost all oc them, even though some are over 30 years old.)
Because my stereo is so old that it only accepts tape or CD as an input. No bluetooth or even USB stick. However, it works, and it's adequate for my humble needs, so I haven't considered replacing it yet.