system
A chat on subreddit /r/NoStupidQuestions
human
There are several, I can only recommend "reddit is fun" or "rif is fun" since that's the one I use. It has the older design, very clean IMO without the excessive bs they force on this app. Also video player works lol. 

Other that I know of is Apollo, should be more customizable with more modern design.
gpt
Thanks, BT!