Firefox-ESR 91.3 doesn't use OpenGL GLX anymore. Instead it uses EGL by default.
EGL requires at least mesa version 21.x. Debian stable (bullseye) ships with mesa version 20.3.5 For the nvidia users the following bug report might be important: https://bugzilla.mozilla.org/show_bug.cgi?id=1737428 It's possible to switch back to GLX. To do this you need to open about:config in FF and then change the entry gfx.x11-egl.force-disabled from false to true Suggestion: Try to change gfx.x11-egl.force-disabled to true maybe it solves this bug. If it does, the easiest solution might be to change the code in a away to make FF use GLX by default again for all upcoming ESR versions. The more tortuous solution would be to upgrade mesa to 21.x in Debian stable and newer nvidia drivers in non-free. Best Regards, Oliver C.
