If you like math challenges and advanced algorithms, there is Project Euler. HackerRank also has AI and math categories. If you are looking for competitions that offer prizes, maybe look for some local in-person or remote hackathon to join?
The activity holder says participants can open source their cases and each submitting will get paid up to 200¥(30$). And final additional award up to 20000¥(3000$) will be given according to rank. However, Chinese bank and WeChat accounts are needed.
Due to open source and possible better ai copilot for Rust, it contribute to Rust. And get paid. Mathematical optimisation algorithms in Rust may also get high score.
In my opinion, the salary is not high enough and I never think AI can really write Rust in the future. However, I'm in University and can only make quick money in this way.