Hello,
Currently running a fresh install of Fedora 35.
I have to AppImages which are trying to open a webbrowser for their user login / authentication process. However, their attempts to open a browser window are unsuccessful. Also the system default browser won’t open.
How can I remediate this problem in order to be able to open the authentication link?
Many thanks!
Welcome to ask 
Have you tried opening a browser from the desktop and not via the app?
Does your internet connection work?
Is the system fully updated sudo dnf upgrade ?
What has been done to troubleshoot?
Posting more info helps us to help you.
Yes, these points are taken care of.
I came across the following solution from a different application with a comparable issue:
https://github.com/Ultimaker/Cura/issues/8094
Solution was to enter:
env -u DESKTOP_SESSION -u KDE_FULL_SESSION -u XDG_CURRENT_DESKTOP /path/to/App.AppImage
However, I get a permission denied error on that command, even when running it as root.