Mozilla Firefox is slow even if hardware acceleration is enabled?

Try enabling gfx.x11-egl.force-enabled in about:config to force the use of EGL¹ and then restart the web browser.
If this works, enabling layers.acceleration.force-enabled can boost your performance even more by enabling OpenGL alongside EGL. ²
This also works on Flatpak if the security permissions are correct (use Flatseal³ if needed).

Tags: #linux #gnulinux #sysadmin #gpu #gpu-linux #gpuacceleration #egl #opengl #x11 #xorg #mozilla #firefox #hack #flatpak #flatseal

https://www.khronos.org/egl/
https://flathub.org/apps/details/com.github.tchx84.Flatseal
https://linuxreviews.org/HOWTO_Make_Mozilla_Firefox_Blazing_Fast_On_Linux