KVM/Qemu and Hyper-V also have snapshots, but hyper-v has a dumb name for them that I always forget.

I wouldn’t recommend it due to complexity, but clevis is a thing. It permits a machine to automatically unlock on boot when various environment conditions are met.

Honest question, what are you using that is only available from snap?

Snap is almost universally despised with host, flatpack and appimage usually being preferred.