I have searched for a bit eventually arriving at well known websites like codeforces, atcoder, codewars, codinggame or the various OJs. They mostly involve solving tasks where usually the main focus is elementary discrete maths + data structures and algorithms.
However, I cannot find any that target the more theoretical side of Computer Science with topics including Complexity, Theory of Computation, Logic, Algorithms, Probability & Linear Algebra questions etc.
So do such contests exists? If so, please list! Bonus if there are any contests for high schoolers as well.