Douban is good for Chinese events, ChengduExpat will give you a good rundown of foreign events but not a great forum since it’s still very new. Find a couple people to drag you into wechat groups that overlap with your hobbies and I’m sure you’ll find likeminded people in no time. There is a guy who does food tours (Jordan, who wrote an article you can find on the front page of this site) who is more well-versed in the local food scene here than most foreigners. But yeah, as far as forums go, most of the conversation has migrated to WeChat…
I don’t have WeChat, but I will download one later and try to get on it if it will allow me access to some of those social events. Are you a Chengdu Native?