I like to review photos with the client on my laptop/Apple TV. So I make all the stars, flags, labels on the laptop. When I copy the dng files to a thumbdrive and copy them from the LR import dialog into my desktop/different catalog - they come in missing all the metadata.
I assumed the reason to use DNG was that there wasn't a need for sidecar xmp files. I assume that somehow I need to tell LR to "bake" the settings into the files because they're only the database?
Are you using Lightroom or other Adobe on your client’s computer or Apple TV to rate the photos? It is up to whatever app you’re using to rate the photos to write the data into the DNG. Depending on what app it is, it may not know what to do with DNGs enough to do that.