Hi Nik: I am doing something similar for a department at UNED (Long Distance Spanish University). I can try to provide you some help regarding PostgreSQL and nginx.
I have been trying to configure PostgreSQL (the version downloaded from my side is 11.7) but when I try to start JupyterHub with this DB, I have an error relating to the need of “psycopg2”. In addition, if I try to install this package, it is needed first to install libpq-dev but I am unable to download and install it following the instructions at https://pypi.org/project/libpq-dev/ so by the moment I am keeping SQLite.
Regarding nginx, if you decide to use it be aware of the following post: Nginx reverser proxy error in configuration template
All the best
Jose