Mitigating skew by using the correct tag

[natterangell]

Hi,

I'm in need of the displaylink driver on aurora-dx, and I've spent hours debugging why GA in my custom template refused to build the kmod-evdi.

After some intensive google-fu I finally realized that the kmod-evdi module wouldn't build unless I declared the negativo repo in the containerfile.

With that out the way I kept pulling my hair out not understanding why the kmod-evdi kernel version didn't match the aurora-dx-stable upstream image kernel.

I finally figured out I needed to declare akmods-extra:coreos-stable-40 as the tag for the kernel to match.

With the gts/stable/latest kernels now being offered in different channels it would be better to make this more evident in the README file. There are quite a few tags in the builder not mentioned in the README (are some of these just for testing?)

Would you like a PR for revised instructions?