I use Hi-Fi Cast to cast my local media to my Chromecast audio’s (over UPnP. In the app I see the artwork, filename, artist and title, but in my chromecast items, I only see the AppStatus channel changing to Casting: filename. All other channles like MediaTitle, Image remains empty. I the Google Home app where you can configure the Chromecasts, I see the fiename and artist (no image or title).
Are these limitations from the app I cast from?
I also see that metadataType is GENERIC, if I remember well, this was in the past MUSIC_TRACK
I can offcourse do some string manipulations on the filename to grab everything I need, but in my old OH2.x I used the channels albumArtist, albumName, artist, title. These are still working.
Maybe try/use anther app?