The problem is that you should have run lxd.migrate when you had both the deb and snap, that would have seamlessly transferred the data over.
The fact that you ran lxd init on the new install doesn’t really change anything, it’s just a clean empty LXD.
I think we could make LXD a bit smarter in lxd recover so that if no type is set, we assume it is containers. @tomp
In the meantime, you could go and edit the backup.yaml by hand to have a type: container inside of the container section. This may be enough to make lxd recover happy.