This covers stuff applicable to Arduino and to other embedded platforms.

• U8g2_Arduino: Arduino Monochrome Graphics Library. Two-clause BSD.
• Ucglib: Color graphics library with focus on Arduino Environment. Two-clause BSD.
• LVGL: Light and Versatile Graphics Library. MIT.
• m2tklib: Mini Interactive Interface Toolkit Library. Abandonware? GPL3.
  • See also this guide from Oli Kraus
• Micro-GUI (ugui): Abandonware? MIT.
• TouchGFX for STM32. Gratis.
• STEMWIN for STM32. Gratis.