One or more network protocols are missing

Recently, a computer (Windows 10) had a limited network connection, and when using the troubleshooter I got “one or more network protocols are missing”.

I’ve tried many software fixes, but not any of them worked. I reinstalled Windows completely, upgraded the UEFI and even reset it, installed an additional NIC and even tried a cable from a PC that had a working internet connection, but the issue persisted.

Eventually I found the problem. It was another network device that was somehow interfering with the network. I unplugged that device from the network, and everything worked perfectly fine again.