@lucyllewy you were right, it was an issue like you described. Just had to place the archive in the right directory
Additionaly, I had problems with the cross compilation which were described and solved already here: Cross compile snap on amd64 to arm
In the end I had to add
architectures:
- build-on:amd64
- run-on:all
to the snapcraft.yaml and needed to execute
snapcraft --target-arch arm64 --destructive-mode
instead. That worked for me