For container orchestration, which is mostly what k8s provides, then you could use docker swarm or nomad.
You could use docker-compose with multiple replicas of the wanted container + a load balancer to divide the load.
In general I don't think k8s/k3s is needed for hosting lemmy yet, but since I have a setup for k3s, it is easier for me to use it.
I have only 1 container of pictrs running(with no scaling) and are using longhorn for storage, so if the pictrs container switches node, then longhorn handles it for me.