To replace the default font, you must use system hacking (similar to "jailbreaking"). Here is the classic method (still used by fans today): symbian s3 default font ttf fonts

If you are experimenting with TTF fonts, here is a troubleshooting table: Share your horror story of the "infinite reboot

The main files include:

Unlike modern Android or iOS, where fonts are relatively easy to swap via themes or developer options, Symbian stored its fonts in the protected system ROM ( Z: drive). symbian s3 default font ttf fonts