When I set my server up years ago all I did was log in on the web interface. Literally as simple as any other service.
They make you register with their own website to login to your local instance... That's you jumping through hoops to accommodate their cloud bullshit;
It’s important to understand that Plex Media Server does not have its own graphical user interface. When you run the server on your computer, NAS, or other device, you won’t see a window open with a “server UI” or similar. Instead, you use our web app to manage your server.
It's so fucking unnecessary.