Ok, I gave it a try and set up a Hyper-V VM with 1x500GB SSD VHDX and 2x direct connected 1TB HDDs. The process is pretty straightforward. Download the Hyper-V VM, unpack and import it, adjust the hardware settings (I gave it 1x CPU and 4GB RAM) and fire it up. The rest is done as known via browser as usual (managing admin account, set up system settings, entering the license key, etc.).
Qnap‘s browser gui is not as „clean“ as Synology’s DSM but good to handle. Some features like creating RAID and volumes seem to be more difficult but you’ll have more options (thick or thin volumes, warning level, over-provisioning, etc.). Although the VM has only one CPU and 4GB RAM dedicated it runs pretty smooth. SMB and rsync transfers are fast as expected.
Next step will be installing some (free) apps.