MMB Hi, that's not the way i did. I downloaded the the original Budgie ISO file https://getsol.us/download/ and mount directly in VirtualBox without any change, except the EFI setting to boot. I used VirtualBox latest version.
If you want to copy partition, you could do with dd or Clonezilla, both should be fine. But then you need to modify little bit to make it bootable. As my previous post, you could modify EFI use macOS, there you see the loader folder. Inside you see a .conf file that tell which partion to boot, also the kernel params... Below is mine:
title Solus 4.0 Fortitude
options root=PARTUUID=8a153890-f560-4258-ab19-0dd20544dbc4 quiet loglevel=3 splash systemd.show_status=false rw radeon.si_support=0 radeon.cik_support=0 amdgpu.si_support=1 amdgpu.cik_support=1 radeon.modeset=0 amdgpu.runpm=0 acpi_backlight=intel_backlight bluetooth.disable_ertm=1
Also you may need to modify /etc/fstab file in partition that has Solus to update correct partuuid (when you copy to other partition, the new partition has different uuid). To modify linux partition, you must use a linux OS. You could try with a Linux Mint Live.
For me i also tried Linux Mint on my Mac and it works fine. Maybe you should give it a try 😉