I haven't been able to find any communities dedicated to our Lord and Saviour Eris, and I am perplexed by this fnord. Where are you hiding, my fellow popes?
It predates Illuminatus!, which came out in the early 70s. The foundational text of Discordianism, the Principia Discordia, was published (i.e. photocopied and sent out to fellow fringe dwellers) around the mid-60s. Illuminatus!, however, popularised it.