also Comcast and other ISP’s have their own speedtest(which they used to use Ookla but have since moved away to their own, speedtest by Ookla just happens to be the standard used these days for speed tests for your ISP as mentioned.) However given that you mentioned to the OP that it may not be Twitch and may be their own ISP, testing with an external source would help determine is up/down speed problems at least exist elsewhere. But you’re right, a ping to the various chat servers might be useful. As a note my own chatbots have been exiting with an ECONNRESET in recent weeks due to some issues as well, which again suggests potential relation(only a hint of course)
If chat servers are disconnecting, chat services would disconnect, so this is potentially related. If you have other background information behind the scenes as to what else might be causing a disconnect from chat programs during the time periods that TwitchSupport is literally saying they’re having trouble with chat services, that data would probably be helpful here.