Just upgraded from Mint 18 to 20.2 and am finding FIrefox unusable. I've tried to research this and am getting nowhere. Ryzen 5, Gigabyte GA-356-gaming MB , 32GB Ram I have about 10 windows configured with 10 tabs. (Happily this version of Firefox now remembers which desktop they are on across reboots!) When I start up firefox and it begins loading these tabs, it grinds to a halt with high CPU utilization and for some reason there is almost no activity on ethernet. The tabs take FOREVER to load, and once loaded firefox windows and tabs operates either clunky or unresponsive. MInt is affected some too, with other operations somewhat clunky. I can reboot and load a session of Chrome and it behaves fine and speed tests there are proper. Since it works on Chrome, I figure this is strictly a FIrefox code issue, not something underlying like BIOS (which is F31, not the highest for this MB) But hopefully there is a Mint work around that someone knows.