RNDIS is the proprietary protocol used atop USB for virtual Ethernet functionality but its support outside of Microsoft Windows has been mixed. It is not y used in cross-platform environments and due to security concerns the upstream Linux kernel is looking to move the RNDIS kernel drivers behind the "BROKEN" Kconfig option so they effectively become disabled in future kernel builds.
Ultimately once marked as "BROKEN" for a while, the drivers will likely be eventually removed from the upstream source tree.
Greg Kroah-Hartman wrote in a commit: "The Microsoft RNDIS protocol is, as designed, insecure and vulnerable on any system that uses it with untrusted hosts or devices. Because the protocol is impossible to make secure, just disable all rndis drivers to prevent anyone from using them again."