Error I can't run this script (Vivaldi - HTML5 Proprietary Media)

Getting to the point, I like a browser (vivaldi) except it’s not available on flatpak, so I downloaded the RPM package from their website and installed it via rpm-ostree. But I need to add proprietary media for everyday use, I need to run a script but this is not possible in Silverblue.
For this it is necessary to enter this page and follow its steps (https://help.vivaldi.com/article/html5-proprietary-media-on-linux/), but when executing the command in the terminal returns me this:

Can anyone help me so that I can run this script and install the proprietary media?

The solution is at this link: https://forum.vivaldi.net/topic/43324/problem-with-html5-proprietary-media-on-linux-fedora-silverblue/22?page=2