Hey folks,
The linked file did restore my thunderbolt ethernet adapter, but you can't just install it as it is --- since the version number is lower than the broken version, OS X will simply ignore it. I had to take a few extra steps to make it work.
1) Disable system integrity protection as described in this article:
http://www.imore.com/el-capitan-system-integrity-protection-helps-keep-malware-away
2) Once you reboot, open a terminal window and move the broken version out of the way with the following commands:
cd /System/Library/Extensions
sudo mv AppleKextExcludeList.kext ~ (this will move it to your user's home directory, just in case. enter your login password when prompted.)
Now that that's done, install the package from the linked file and reboot. When I did that my thunderbolt adapter started working again, no reconfiguration required.
If everything's working, you can clean up as follows:
1) Open a terminal window again, and type "sudo rm ~/AppleKextExcludeList.kext" (and enter your password again if needed)
2) Reboot into the recovery console and re-enable system integrity protection as described in the above article.
Hope this helps.