How to run ipykernel from jupyterlab

I am working on setting up jupyterhub in Kubernetes. I have followed zero to K8s document → Setup JupyterHub — Zero to JupyterHub with Kubernetes documentation to setup it.

I have successfully launched the jupyterhub and it server spawn is also working. But when launching jupyter notebook and selecting the kernel it says

**Error Starting Kernel Invalid response: 503 Service Unavailable**

When did kernelspec inside pod got this info:

jovyan@jupyter-etuyhf:~$ jupyter kernelspec list
0.00s - Debugger warning: It seems that frozen modules are being used, which may
0.00s - make the debugger miss breakpoints. Please pass -Xfrozen_modules=off
0.00s - to python to disable frozen modules.
0.00s - Note: Debugging will proceed. Set PYDEVD_DISABLE_FILE_VALIDATION=1 to disable this validation.
Available kernels:
python3 /home/jovyan/.local/share/jupyter/kernels/python3

How to resolve this?

How to successfully launch the Kernel in jupyterlab when setup is on kubernetes?
Following are the error screenshots: