Actually both should work. The problem in this case is probably that the package requires python3.6 and thus cannot be found using a python 2 pip. I changed the README for consistency though.
Sorry thats my bad. The package is written in python 3. Thus it is also possible that you have to install the package using `pip3 install simple-gpu-scheduler`. If the command pip3 does not exist try installing python3 using the ubuntu package manager apt.
Installing Slurm requires root access to the server/workstation, which is not always available. In academia the management of computational resources is often the responsibility of a separate IT unit which is not part of the research group itself. Further the IT unit might not be willing to implement desired changes to the server infrastructure or might take _extremely_ long to do so. Often the setup of a scheduler is also significantly more complicated in this context, for example due to authentication via a University LDAP or oddities of the server setup.