I’m a bit confused what the question is here.
As I wrote above: on computers where you simply want to watch, open a web browser and point it to https://app.plex.tv
Don’t visit that /link URL anymore, unless you need to connect another smart TV client.
As for the QNAP issue, I’m afraid I can only give you this, as I don’t have such a device myself: Qnap faq.....read me first!
