While I believe I have seen this yesterday already, I also believe this request got deleted.
I'll take the risk and answer here hoping I'm not doing anything wrong.
I don't understand three things:
A) Where is the problem to download something not having a QR code? You have an URL and can just download it with your computer. I download many files from the internet every day and have never used a QR code for this.
B) Why don't you paste the URL into some of the hundreds of free QR code generators online if you want a code so badly? It works and will even download with FBI right on the 3DS.
C) What are you planing to do? As far as I know the Discord client for 3DS didn't get updated anymore and will not even work. See
here.
[Not that I have any knowledge myself never having used Discord]