Today I found a potentially interesting way to contact mainland Chinese. I found a Chinese language exchange Discord chat room. At the time of day I happened to drop in there were few Chinese online, but it was pretty late. I was able to have some brief discussions in Chinese. Overall the server seems pretty active, and I intend to come back when more people are likely awake in China. The Discord crowd seems pretty young, but also pretty genial and earnest. Also it is interesting to learn that at least some people can access Discord from inside China.
The most memorable conversation, sadly, was in English, and was between a French girl and Winston (a Chinese high school kid) about plastic surgery. Winston was all about getting eye lid surgery, and the French girl was trying to tell him everyone is uniquely beautiful in their own special way and Chinese girls are considered hot in France.