KataGo AI for Ultimate Tic-tac-toe
https://en.wikipedia.org/wiki/Ultimate_tic-tac-toe
This AI includes a widely-accepted additional rule: If one should play in a finished (win, lose, or filled) sub-board, then he/she can play everywhere. It has been proved as first player win without this rule.
This AI supports both with and without “Tiebreaker” rule.
Tiebreaker: If no one connects 3 subboards, then who own more subboards wins.
Results:
With Tiebreaker: First player 70%, Second player 14%, Draw 16%
Without Tiebreaker: First player 33%, Second player 11%, Draw 56%