Hmm, I will get back to you with how I did this but as far as I remember by installation had some permission issues.
You can try SSHing to the server and there should be a virtual environment setup in the folder where JupyterLab was installed (/opt/jupyterlab). I vaguely remember activating the virtual environment and trying to install plugins from there or fixing the permission issues.
I will get back to you within a couple of days with exactly what I did, but if you want to you can go ahead and try it yourself.