Windows – Can’t Drag’n’Drop files in VirtualBox from guest

Have you tried using "Bridged Networking" network card settings for the guest operating system?. "Bridged Networking" option provides sharing the network interface between the host and guest operating system.

Ensure, you have configured Network adapter settings as "Bridged Networking" and try accessing the shared network path.

Also, ensure the local windows firewall is not blocking your network connection. Do ping check from guest OS to host and ensure it is responding. To isolate the issue, disable the Firewall for a moment and check the shared path accessible.

Hope this helps.

There are no guest additions for Mac because macOS is not supported to be run as a guest in a virtual machine on a system other than macOS. In your setup, Ubuntu is the guest system and macOS is the host system.

The guest additions are to be installed in the guest system. Just start your Ubuntu virtual machine and select Devices -> Insert Guest Additions CD Image from the VirtualBox command menu to install the guest additions into Ubuntu. After that, copy and paste should work, provided that you activated it in the settings as you described.