Hi!
Please check this C example:
Fonts: https://github.com/sharandac/My-TTGO-Watch/tree/master/src/gui/font
Usage: https://github.com/sharandac/My-TTGO-Watch/blob/master/src/gui/mainbar/main_tile/main_tile.cpp#L69
Doc: Fonts — LVGL documentation
Other solution is loading fonts dynamically from device FS:
https://docs.lvgl.io/master/overview/font.html#load-a-font-at-run-time