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This is along the lines of what I'm looking to do. In Mojave I turned off SIP, went in to the System Fonts folder and deleted the unnecessary fonts in there. Now that Catalina has the drive set as read only, struggling to figure out how to move those out of there again. My first attempts were to start up off a USB Catalina Installer drive and use Terminal to cd to the folder. I got to where I could ls my HD from the bash prompt but a bit unexperience to then drill down into the System folder and then I guess I'd have to rm each font? Not even sure if that would work. There are 332 files in that folder. I only need 18. It was easy before because I could see and drag in the Finder. Got to be an easier way.