Ubuntu 20.04 pre-installed firefox lagging on scroll in fullscreen mode
I have also found that disabling smooth scrolling in preferences solves the issue, even when fractional scaling is enabled.
This error only occurs when fractional scaling is enabled. If you disable it everything works fine.
check in its preferences that « hardware video acceleration » is enabled, and in about:config set « layers.acceleration.force-enabled » to true
sources :
https://discourse.ubuntubudgie.org/t/firefox-scroll-lag-on-ubuntu-budgie-19-04/1783/2