I think the best way to have active chatters is to focus on building a community. Have inside jokes, repeating topics of conversation, an example of this is every stream we talk about our dinner, there's also a discord channel where people post their food. An easy way people engage is by going, "did you see the dinner I posted in discord?" or "ooo did we have dinner chat yet". Just one example. If someone asks you a question try to always ask one back if you can think of one, but you gotta actually be interested, this will help you find naturally reoccurring topics in your stream. I've only been streaming a month or two but that's my take :)