I've got an second hand notebook at work with low specs and installed Ubuntu 18.04. The GPU is very old and every effect makes the whole system lag. Is ther any way to reduce UI effects to improve performance?
A reasonable improvement you can make is disabling animations, and this can be done without a tool, directly from the command line:
gsettings set org.gnome.desktop.interface enable-animations false
To reverse this, just:
gsettings set org.gnome.desktop.interface enable-animations true
This can also be toggled from
gnome-tweaks, referenced in the accepted answer.
Although going manually through the
gnome-tweaks tools and the
dconf-editor works, the
gsettings commands as in the other answers did not work for me, in a programmatic/CLI approach on Ubuntu 20.04 Focal Fossa.
What did work for setting this up beforehand on VMs in the cloud with XRDP was:
dconf write /org/gnome/desktop/interface/enable-animations false