How do you identify how someone got to the community page?

I’d start there if you can. It will do most of the heavy lifting for you in terms of the source of traffic and other behaviors. 
 

Maybe there are other options, but I’m not aware of them. 
 

if you have a tool for site analytics like that, you can also append UTM parameters on the end of urls when you link to the community from elsewhere. They will allow you to specify the source and/or medium of the traffic. But you need something like Google Analyitcs to read that. You won’t see any of that type of traffic data from Gainsight DH; just the audience dashboard.