ERR_EMPTY_RESPONSE?

My Config: Ubuntu 16.04 LTS Disk

I'm going through the "Host a website" tutorial: https://www.linode.com/docs/websites/hosting-a-website-ubuntu-18-04/

I've gone through all the steps before the DNS config section, but whenever I try to access my IP: 198.58.106.248 I get the generic ERR_EMPTY_RESPONSE error. I've double checked all the configurations and the steps in the guide, everything seems correct. How would you go about troubleshooting this?

Obviously the first thing that jumps out is that this guide is for Ubuntu 18.04 while I'm on 16.04, would that make a difference?

I also haven't yet connected a domain, so in my /hosts file instead of 198.58.106.248 hostname.example.com hostname I have 198.58.106.248 [myhostname] is that an issue? (I don't know what to put in instead)

Thanks.