The message "No deletable fonts found. To add your custom fonts, place them in one of the following directories" is ultimately a helpful nudge. It reminds you that professional font management requires separation of system-critical assets from personal creative assets.
ln -s ~/Dropbox/MyFonts ~/.local/share/fonts The message "No deletable fonts found
Distributions from before 2015 may use ~/.fonts/ instead of ~/.local/share/fonts/ . Try creating the legacy folder: The message "No deletable fonts found
In File Explorer, go to View > Check the box for Hidden Items . 💡 Pro Tip: Management The message "No deletable fonts found