If you prefer working with RStudio or JupyterLab in dark mode, you can alter the existing settings. However, it is important to recognise that once the workspace is fully reloaded (either the session disconnected or you leave and re-enter) you will have to alter the appearance setting again.
In RStudio this is done through the following settings:
Global Options >
In JupyterLab, it is arranged as follows:
JupyterLab Theme >
(Hint: The editor theme "Cobalt" in RStudio is very pleasant to work with)