According to 9-to-5 Mac
Font management is getting a major upgrade on iOS 13. It will not be necessary to install a profile to get new fonts into the system anymore. Instead there will be a new font management panel in Settings. A new standard font picker component will be available for developers and the system will notify the user when they open a document that has missing fonts.
It's about time. I say this as both an iPhone and (especially) iPad user and as a font maker. There have been ways to do it, but nothing officially supported or that normal users would put up with.