[solved] The functionality has been restored.
[2. Update] Workaround: Use Ctrl+C to copy the desired text to the clipboard. Press the “Esc” key twice in a row. Paste the text from the clipboard as usual using Ctrl+V.
[Update] Currently, there may be issues with copying and pasting entire cells in Excel files edited in a browser via TUD SharePoint. This issue is related to the September Microsoft Office patch.
The issue has already been resolved in the local Excel client versions with an update. If you can edit the file in the local Excel application, we therefore recommend using it.
Thank you for your understanding.