> Using custom fonts in Big Sur
How can I use my own Gill Sans and other fonts rather than Apple’s standard set in Big Sur?
You can install your own fonts in Big Sur, but can’t remove those installed on the System volume, which does include Apple’s own version of Gill Sans from Monotype. Making such changes to the Big Sur system is technically difficult, and involves irreversible loss of security protection, which would be a major sacrifice.
To install and use a replacement, you can either use the bundled Font Book app, or a professional font manager such as Extensis Suitcase, which is best for those who have many additional fonts, particularly if you use Adobe and such. The current release of Suitcase Fusion is compatible with Big Sur, and runs on M1 Macs.
For more modest needs, Font Book supports both libraries and collections, the latter being preferred to gather together your most used fonts, so that you can choose without having to scroll through thousands. Font Book can also resolve duplicates and validate any font you have installed. Those features, and the ability to disable and remove fonts which aren’t locked on the System volume, are all available in the contextual menu when you Ctrl–click any font name listed in Font Book.