All my text is microscopic and there is no longer a font management add-on for this version.
Firefox did the same thing two years ago - entirely new format, jettisoned "legacy" apps and add-ons. I resisted, went to the enterprise version and when that went to the new version, shut off my updates and lived with no security fixes (have a pretty strong firewall and business-strong anti-virus; it's my personal computer connected to the company network). When WIN 7 support ended last January, I was forced to update to WIN 10 and had to give up on legacy Firefox. I finally found some code to bring tabs back to the bottom (FF refuses to allow it as a freedom choice) and it now works pretty much as I want it.