To easily copy files from a local Mac to a MacOS virtual machine in UTM, use file sharing, which is a simple and reliable method.
Enable File Sharing on the Mac hosting the virtual machine and access the local Mac's files through the Finder in the virtualized MacOS installation.
Connect to the local Mac from the virtual machine over the network, locate the files you want to copy, and drag and drop them into the virtual machine.
File sharing provides a consistent way to transfer files between Macs in virtualization software, and it can be used to copy files to Windows or Linux virtual machines as well.