snapd on Debian requires sid( unstable ). So would not work with any of the official images, unless back ported.
There are many ways to achieve the same end goal. Involving chroot, BSD like jails, etc. The idea of containerized apps has actually been around a long time, and probably started originally with Solaris. Debian has also picked up a lot of Solaris-isms in the past such as zfs, zraid, etc. So it is possible that Debian also picked up the original concept of Solaris containers. But I’m not sure.
One of the things that throws me off this whole Ubuntu core thing is that first, It’s Ubuntu, and Ubuntu is Canonical. Second, it requires “registration” online which I think is absolutely unnecessary and potentially insecure. With databases being cracked, and hacked all the time. Additionally, and I am not 100% sure of this. But it seems that Canonical s idea of monitizing Ubuntu has crept into Ubuntu core. e.g. you search for something on the local system, and the system feeds you adverts back from the internet as well . . . which is stupid, and crazy.
By the way, the Linux kernel is, or can be thought of as a single executable. So it would not be impossible to containerize the kernel as well. Usually, this is done for debugging purposes, and it may not be possible to abstract out the hardware properly. However, I think in this case. Personally, I would do something like a chroot jail snap . . . but that’s just me.