New user here, today tried installing opnsense 21.1 ISO to Hyper-V Gen 2 VM, 127 GB disk, secure boot disabled.
Found archived reference to what is apparently the same issue: https://forum.opnsense.org/index.php?topic=10136.0
I found that two responses in that post helped me: Ctrl+C and sign back in as installer, and I had to do this twice. Once at "Select Task" and once at the prompt to create default-sized swap file.
Just posting to help keep the issue alive.
I have a similar setup but I have had success getting OPNsense installed. I did have to use the CTRL+C trick once, but the install finished after that.
My Specs:
Gen2 VM
2 vCPU
1024MB RAM (uncheck dynamic memory)
16GB disk
I attached the ISO to the DVD drive of the VM, booted it, and installed.