The best alternatives to Impossible Tic-Tac-Toe are Mighty Signal, Tic-tac-toe for Slack, and RealTimeToe. If these 3 options don't work for you, we've listed a few more alternatives below.
What do you think of Impossible Tic-Tac-Toe?
Snowflake Startup Challenge— Win investment & global exposure with Snowflake and NYSE
I found an interesting solution for the problem of not having tic-tac-toe in Slack with the use of Slack Buttons. The app is Serverless and almost stateless running on AWS Lambda which costs me about $0.30AUD/month to support over 600 hard working Slack teams. Someone told me that Slack internship candidates are asked to make tic-tac-toe. 😂