iCloud ubiquitous container not writable from Finder

Hi,

my iOS/macOS app uses iCloud drive to store files. Everything works correctly on iOS / iPadOS:

Files can be created, moved (to and from), opened, etc. Even in the macOS terminal the same things are possible.

However, using the Finder on macOS (Catalina and Big Sur), the cloud container is not writable for files, ie. no files can be dragged and dropped into the folder.

Dragging or creating a folder works fine and includes the child files. Dragging a file into a subfolder will again result in a "no entry" mouse cursor and file cannot be dropped.

How to fix this so that in the Finder, files can be moved to the container?

Code:

let containerURL = FileManager.default.url(forUbiquityContainerIdentifier: nil)
let documentDirectoryURL = containerURL!.appendingPathComponent("Documents")
let documentURL = documentDirectoryURL.appendingPathComponent("myFile.txt")
let text = String("test message")
text.write(to: documentURL, atomically:true, encoding:String.Encoding.utf8)

My info.plist settings:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
	<key>iCloud.ALS</key>
	<dict>
		<key>NSUbiquitousContainerIsDocumentScopePublic</key>
		<true/>
		<key>NSUbiquitousContainerName</key>
		<string>ALS Levels</string>
		<key>NSUbiquitousContainerSupportedFolderLevels</key>
		<string>Any</string>
	</dict>
</dict>
</plist>