I successfully installed NetBSD 10.1 on an Intel Mac Mini and it runs well. However, I have trouble using my old Thunderbolt 2 dock. If I connect the Mac Mini with a Thunderbolt 2 cable to the dock with the monitor, keyboard and mouse and Ethernet network all connected to the respective ports on the dock, I cannot interact with the machine. Connecting everything directly to the Mac Mini works perfectly.
This brings me to the question: Does NetBSD lack Thunderbolt support?
EDIT: The answer is: Limited Thunderbolt support exists.
After complete shutdown and connection of all peripherals to the Thunderbolt dock, except the monitor, the machine booted normally and keyboard, mouse and wired network were usable. However, I could not get the monitor to work over Thunderbolt. There seems to exist some limitations for which I was unable to figure out the cause. The direct HDMI connection to the Mac Mini works well, but the HDMI port on the Thunderbolt dock cannot be used. Apparently, video over Thunderbolt is not supported.