EDIT: Just realized today that I was using the wrong kext. I should have been using AtherosE2200Ethernet.kext. Got bad information from a guide elsewhere on the net and kept going with it. Internet works now, I learned a lesson!
Sorry for such a long post. Thanks so much for this guide. I am a total beginner and I have been struggling on my own for two days trying not to ask for help. I was able to figure out a lot on my own because of the great resource here at tonymacx86. However, I'm on my third installation on El Capitan, and I just can't get ethernet to work. I've been avoiding asking for help, because even though I would love for someone to build me a fire to keep me warm tonight, I also want to know how to build my own so I can be warm tomorrow. After more than 36 hours of work with only 4 hours of sleep, I'm at my wit's end, and possibly my body's, too. I hope someone can help me out.
I do not have the H270N-WIFI, I have a GA-Z270MX and a 7700k. I know the motherboard is different, but the chipset is the same, both use Intel E2500 ethernet. So I figured the guide here might apply. Please tell me if I'm being ignorant. I'm also installing El Capitan, not Sierra, because my Macbook Pro is too old to download Sierra. I was able to install El Capitan without a problem using Unibeast. System boots up fine. Nothing really works yet, so I can't test much. First, most important thing is ethernet, so I can get my files transferred over on my LAN and follow guides more easily with copy paste ability to fix the rest of the problems I likely have.
I followed this guide to a T, with one exception being XHCI-200-series-injector.kext. Partly because I actually do already have working USB 2.0 ports after installation. Also, partly because I couldn't find the kext in the repo. I tried to select clone for download, but I think my version of Safari is too old because I see a warning that it is not supported. Aside from that, I was able to follow this exactly and it really helped me understand a few things in Clover Configurator. I'm just left with figuring out my ethernet….for now. Oh, one more thing, I have system definition of 14,1 because I tried 17,1 and I couldn't boot after switching it. I did not perform a clone, so I had to to reinstall El Cap for the third time! Aaahhhhh! (pulling hair out)
One thing I noticed is that during the install, I was unable to select ethernet as my internet connection type. I did try it and the installer crashed. I assume that's because I don't have a working ethernet port. So for each subsequent install, I selected the option for "this computer does not connect to the internet". Now, even after installing the IntelMausiEthenet kext, if I go into network prefs and try to ad a network, it gives me an error and won't let me add anything. The ethernet port is not working anyway. At least there are no lights when plugin in my cable.
Ataching files here for troubleshooting. I know your guide says to use 17,1, but I tried 17,1 on my last attempt and I couldn't boot afterward. So, I set it to 14,1 this time, which worked before.
Edit: update config and IOReg