Minimal kernel version for full snap confinemenet

A few years ago, I believe there were some bits for full snap confinement that were not in the mainline kernel. Is that still the case ? If not, then whats the minimal Linux kernel version that supports all snapd specific confinement features ?

We need to know this because we are in the process of choosing a hardware to run Yocto based image on which snapd will also run and want to make sure we dont get bitten by this later.