Related to these 3:
I've installed Firacode using every method I can find, but RStudio can't detect it (It's not available in Tools -> Global Options -> Appearance). I've tried all the fixes in the three links above, but nothing has worked. I've restarted RStudio and my computer. fc-list | grep "fira" returns the path to several OTF files in /usr/share/fonts/opentype/firacode
Any help is greatly appreciated! I'm working on reading through the RStudio source code to see where fonts are loaded, but I don't know java, so it's been slow. If anyone has found another way to get this to work, I would love to hear it!