If you don‘t want to go through the installation process, you can find pre-built Windows 10 Qcow2 images shared by independent developers. These are popular as they save time, but you must exercise caution and trust the source.
Although VirtualBox doesn‘t natively support Qcow2 files, you can still use one: Windows 10 Qcow2 File WORK Download --BEST
In Proxmox web UI:
, pointing the storage to your new QCow2 file and the boot media to your ISO. Optimizing Windows 10 for QEMU/KVM Performance If you don‘t want to go through the