One way is to buy Oneplus/Xiaomi device and flash a custom AOSP-based ROM. Most Oneplus & Xiaomi devices esp. those with Qualcomm SoC enjoy pretty decent custom ROM development. Plus in both warranty is NOT void if you unlock the bootloader and root and/or flash a custom ROM. A few financial apps or even games might be problematic. GCam can improve imaging quality in certain cases but it could be that all cams might not work, front cam could operate at a reduced resolution etc.
Otherwise Pixels obviously and Moto devices with near stock Android.
Edit: In Redmi devices CA is usually limited, 2CA mostly. I don’t know if it has improved off late.