Using fonts
How can I use a font I registered?
A registered font is installed on your device (iPad or iPhone). You can use it in any third-party app that lets you choose fonts.
You cannot change the system font of iOS itself.
Even when it is registered correctly, the font does not appear in “Settings > General > Fonts”. The font is registered on your device as a profile, and you can use it in third-party apps even though it is not listed under Fonts.
You can see what is installed in “Settings > General > VPN & Device Management”.