Turns out that it is actually working. No idea what the question marks are about. I reinstalled Npcap and elected not to install the loopback adapter, since it did not seem necessary for this purpose. I was thinking maybe that confused Kiwi, who knows. In the end, I don't believe removing the loopback had any impact at all, except now the question marks have been replaced...by slightly fewer question marks. It is worth noting that the dropdown menu actually has 2 choices, although they are both blank. My machine only has one network adapter (no IPv6 tunnel adapter), so not quite sure why there would be multiple choices. The important thing is, choosing the first one works (i.e. packets are transmitted and received at the other end), and choosing the second does not (i.e. packets are not received at the target end).
The dropdown menu actually shows two options (both blank) and each is selectable.
The first option looks like this, and works as intended (spoofing)
The second option looks a bit different, and doesn't work (no packets at the target)
