I have put this in the sedan section as I think more people are likely to respond even though I own a 2020 Forte5.Same entertainment system I would wager. Anyway my display sometimes displays cover art when I play an album and sometimes not. I am using a USB stick with albums arranged in folders by genre/artist/album and search for albums by folder names. All album folders contain cover art labelled folder.jpg. I am wondering if it doesn't display if the jpg is either too low or too high in resolution.
Looking at the albums that show cover art and those that don't I find examples of both that are around 28-30kB so I don't think the resolution of the images is the issue
The answer as I stated is that album art as to be embedded. I found software Tagycardia that was able to embed the album art into the track tags. Previous to this my album art was a jpg file in each album folder, which served me well for purposes I used on the computer but not the car.