https://www.digitalocean.com/community/tutorials/how-to-serve-flask-applications-with-gunicorn-and-nginx-on-ubuntu-18-04#step-6-%E2%80%94-securing-the-application says for running a flask web application with gunicorn and nginx with https:
Certbot provides a variety of ways to obtain SSL cert...
@JohnnyApplesauce Better to move the script to a dedicated directory under your home directory (dedicated, that is, to your own private executables), maybe ~/bin. Then set $PATH in your shell's startup files: PATH=$HOME/bin:$PATH.
@JohnnyApplesauce In general, do not touch /usr/bin. Your system and its package manager would get severely confused if you accidentally started moving, renaming or overwriting files there.
@StephenKitt Might it be worth mentioning that some things are documented in several sections and how to view the manual for a particular thing in a particular section, e.g. man 1 printf vs. man 3 printf?