Managed to get it working with random icons with this in the Info.plist in the main app bundle
<dict>
<key>UTTypeConformsTo</key>
<array>
<string>com.apple.icon-decoration.badge</string>
</array>
<key>UTTypeDescription</key>
<string>Stared Item</string>
<key>UTTypeIconFile</key>
<string>mvstar.icns</string>
<key>UTTypeIdentifier</key>
<string>com.sk.mvapp.xxxxxFP.Provider.star</string>
</dict>
Then add the icns file in the xcasset or the main app folder
Also double check that your file really has the decoration tag with fileproviderctl evaluate
Topic:
App & System Services
SubTopic:
Core OS
Tags: