Kubernetes - how to map docker run command-line parameters to kubectl command line

When you define pod spec for your sage you can define both command and an args array, so for you it would be like

command: sage
args:
- -notebook

for launching with kubectl run

Usage:
  kubectl run NAME --image=image [--env="key=value"] [--port=port] [--replicas=replicas] [--dry-run=bool] [--overrides=inline-json] [--command] -- [COMMAND] [args...] [options]

so try running with -- delimiter : kubectl run --image=sagemath/sagemath --port=8080 --type=LoadBalancer -- sage -notebook