I just noticed that Apple updated the Font Book app in macOS Ventura, and while I don't know for sure, it seems that it was done in Swift UI. It's nice!
Here's what I wrote a few days before WWDC this year:
WWDC wish: Font Book comes to iOS and iPadOS. they tried a complicated and overly-cautious solution a few years ago and uptakes seems to have been close to zero, and completely worthless even to people like me who love fonts.
Major rethink needed.
For example, when I buy a font today, I get an OTF/TTF file which I can double click on macOS and start using it everywhere in the system immediately.
On iOS/iPadOS I need to download a shady app from the App Store, load the font file, generate a custom profile, install that profile that iOS warns me is scary, and then the font is…still not available in a bunch of apps for some reason.
iPads especially are supposed to support creative pros…this is table stakes.
I would like to think that this rewrite for the Mac will enable them to bring the app to the iPad next year, but we'll see. As it stands today, in iPadOS 1q6, font management is still somewhere between impossible and exceptionally impractical.