allow private servers - you can still have competitive play, just with people you trust to not cheat
anti-cheat on the server only - would require human moderation as well (users could submit reports, which could be compared to server logs)
increase cost for cheating - maybe have players ante up, and lose their ante if they’re caught cheating (e.g. pay for game licenses and have the license revoked); to be fair, this would require independent review