It turns out that even though successfully built they don’t actually work as intended (via bug reports).
I don’t have the means to test them myself, so just want to clean up the offerings and stay with amd64 for now. Be sure to leave all the amd64 builds please.
you have to do this yourself, close all channels that contain them, then re-release the revisions only for the architectures you want …
to make sure new automatic builds do not re-publish these arches again, add an
architectures: entry to your snapcraft.yaml that only contains
build-on:statements for the arches you want.