Recently while in a forum about PPC Macs in MacRumors, a developer ( zgxSystems) posted a means to make FireFox faster...as well as Supported Browser Families -
Firefox Waterfox Arctic Fox TenFourFox SeaMonkey Pale Moon Basilisk.
.and yes it included Linux systems.
Ive applied it to Pale Moon in Slitaz...and it seems to work. Though I have yet to test it more fully.
The process is to add their 'prefs.js' file.
I know it seems unlikely that pref changes would make a difference...but try it and see what you think.
They claim:
Shortened website loading times ... Accelerated content rendering speeds ... Fluid page scrolling ... Reduced disk, memory usage ...
Plus, enhanced user privacy and browsing security!
You can find the files including a explanatory Pdf at:
https://forums.macrumors.com/threads/foxpep-a-faster-firefox.2209108/
..be interesting to see if improvements are made generally.