CD’s are still relevant and for a physical CD you need a DDP image, a 100% error free image of the CD that needs to be send directly to the CD factory* . On this DDP image is not just the audio, but also all information like CD text, ISRC codes and UPC/EAN codes. This means you need to prepare that in advance so that things will go smoothly. I have made and excell sheet where you can fill out all this information, which you can download here.
* When the CD factory doesn’t support DDP images, go somewhere else. There is NO excuse for not supporting DDP images.