Additional fonts can be generated with the tool available on GitHub:
https://github.com/lvgl/lv_font_conv/
The tool runs on Linux. If you do not have a Linux machine, you can use WSL: https://ubuntu.com/wsl
You will also need Node.js installed on Linux:
https://github.com/nodesource/distributions/blob/master/README.md
Here is an example command that has been used to generate the bin file used in the ZSOM GUI example:
lv_font_conv --font /home/someuser/Shardee.ttf -r 0x20-0x7F --size 26 --format bin --bpp 4 -o /home/someuser/Shardee.bin