SageMath kernel only using one core


I have an ProxMox Server with 10 Cores / 20 Threads and 96GB RAM.
I installed JupyterHub, JupyterLab, Notebook and SageMath on an Debian11 LXC with two uses and automatically generated configuration, works pretty well.
I basically installed to use SageMath on my Server with multiple users and to simulate faster than on my laptop. But the problem is that SageMath is always only using one core and is very slow.
I even tried running the Bernoulli Function since it said that this should always run with multithreading but doesn’t work either.
Now I don’t which of the software parts is responsible for it and how to fix it, so I hope someone can help me.
Here I documented how I installed it step by step: Jupyter - FlowerHouseWiki

Can you show us your full configuration for JupyterHub and JupyterLab/notebook/kernels with secrets redacted, as your linked wiki doesn’t show what you’ve changed.

You’ve mentioned LXC but you haven’t said how you’re using it.

Hi @manics,
what do you mean how I’m using it? Me and an few friends want to use SageMath for our studies.
I haven’t changed anything until now, I installed it, generated the config “jupyterhub --generate-config -f /etc/jupyterhub/” and created two users.

Hi! Ideally you should provide enough information for someone new to reproduce your problem.

In your original post you mentioned LXC, but you haven’t said anything about how it’s configured to work with JupyterHub.

@manics Its a Proxmox LXC with latest Debian11 (amd64), 4 CPUs (can be increased), 4GB RAM (can also be increased, but I didn’t because it isn’t even using half of it) and nesting activated.
Hope this is what you meant.