You can select custom font for displaying plain text, date and time, weather, RSS news or name days via web interface – menu
Native fonts on Android 4.4 and older
On older Android version (< Android 5), only three default fonts are available: sans-serif, serif and monospace. Default font is sans-serif.
Native fonts on Android 5 and newer
On newer Android version (Android 5+), all fonts installed in Android are available in Slideshow. The exact list depends on the particular Android image, but usually contains 15+ fonts preinstalled. On most devices, same font might be installed under two or more different names.
If you would like to use font that isn’t bundled in your Android image, you can upload it via web interface, menu
Fonts. Supported font formats are TrueType (TTF) and OpenType (OTF). You can then pick any of the uploaded fonts in the Edit item form, they are marked with an asterisk before their name.