This error code usually occurs when you try to delete or move a file that is in use by the system or an application. It can also be caused by corrupted files or permissions problems.
It sounds as though you have tried most of what I would have done!
If you run out of ideas, you may need to disable System Integrity Protection (SIP), which is a security feature that prevents unauthorized changes to system files and folders. However, this is not recommended unless you are confident about what you are doing, as it may expose your Mac mini to potential risks. To disable SIP, you need to boot your Mac mini into recovery mode by restarting it and holding down Command-R until you see the Apple logo. Then, select Utilities > Terminal from the menu bar and type csrutil disable and press Enter. This will disable SIP and allow you to delete or move any system files or folders. After you have done that, you need to re-enable SIP by booting into recovery mode again and typing csrutil enable in Terminal.
If that doesn't help, come back to us.