Another interesting variant is incomplete information Tic Tac Toe which was posted by SMBC: https://www.smbc-comics.com/comic/incomplete
After thinking about it last night, I made a quick version this morning, and I think it's fun to play as well: https://eapl.me/incomplete/
Another interesting variant is incomplete information Tic Tac Toe which was posted by SMBC: https://www.smbc-comics.com/comic/incomplete