I read a QR code...

qrify.com .. qrco.de .. LOL losers can't even make their own QRcode.. And then I don't go to the site.

Athanoks Barcode Scanner on #FDroid is really nice. Despite it's name the android application both scans and generates 13 standards, including common ones like #QR_code.

https://f-droid.org/en/packages/com.atharok.barcodescanner/

It also has a history so you can look scanned data back(you can disable it)

Barcode Scanner | F-Droid - Free and Open Source Android App Repository

An open-source app that allows you to read and generate barcodes.

As for commandline in linux, qrencode works well for me, but it's commandline.(and easy)

I have a program that selects amongst a bunch of scripts and one of them qrencodes and displays the current clipboard.

I also see GUI applications in pacman
(qtqr) https://launchpad.net/qr-tools
(decoder) https://apps.gnome.org/Decoder/

NOTE linux users usually use their distros in-built installer to install stuff. (Well maybe *maybe* the docker link, but even there.)

QR Tools in Launchpad

Launchpad