Right-mouse-button clicking on any transaction in Transactions tab and copying address, label, and so on, results in the following message in the debug.log:

GUI: Data set on unsupported clipboard mode. QMimeData object will be deleted.

The copied content is actually getting copied to the clipboard, so no problem with the feature itself, just with the log getting filled with unnecessary messages. I don't know if the issue was present in previous versions or if it's system specific, just noticed that today when I was observing debug.log live when submitting a new transaction.

Bitcoin Core v0.21.0
MacOS 11.2.3