AES is far and away the most heavily scrutinized encryption algorithm in history. Of course that doesn't make it flawless, but the level of genius that the authors would need to hide a backdoor in it for all these years boggles the mind.
The implementation of AES in popular CPUs? Yeah, who knows.
Yeah, I would not even go as far as AES in your CPU. Just... any part of your CPU, or your motherboard, or your GPU. RISC-V is still not suitable for desktop, or at least not commercially available AFAIK, and POWER9 is too expensive. I want open software and open hardware!
The implementation of AES in popular CPUs? Yeah, who knows.