these days, i'm hip-deep in canonical stuff, working with ubuntu
core and snaps (boo! hiss! oh, relax ... :-), and i chanced across a
somewhat-neglected layer that supports adding snaps to a basic YP
build, so i forked a copy, tidied it up, and verified that i can build
a core-image-minimal for qemux86-64 that supports adding and running
your basic "hello, world" snap.

here's my current version of the layer (branch snapd-2.55.3, soon to
be updated to snapd-2.55.5 as soon as this current build finishes and
runs):

https://github.com/rpjday/meta-snapd/tree/snapd-2.55.3

the README there needs to be cleaned up as much of that is no longer
necessary, since i added a "snapd_on_yp" DISTRO that centralizes much
of the essential config settings.

so if you wanted to play with adding snaps to your established YP
build, give it a try. still lots of tidying up to do, but it seems to
work.

rday