Sometimes when I open Firefox, the content of Firefox window doesn’t render at all, it gets a frame from the window behind and render nothing else. This issue seems relatively random as multiple open/close cycles seem to temporally fix the issue.
I run Kubuntu 21.10, KDE plasma 5.23.4 on my laptop (X11 session).
>Solution :
In the case where you have only Nvidia card, you can try the solution in the other answer.
Turns out it has something to do in the case when you disable the Nvidia card and use integrated graphics. Firefox seems to be trying to render through the disabled GPU. To fix add this to your .profile:
if ! grep -w -q nvidia <(lsmod) ; then export
__EGL_VENDOR_LIBRARY_FILENAMES="/usr/share/glvnd/egl_vendor.d/50_mesa.json"
fi
logout then login and the problem is solved.