For embedded systems, LVGL is a powerful fully open-source UI library. It is free for both personal and commercial projects, making it a go-to for developers building HMIs on microcontrollers (MCUs) or MPUs.
For teams prioritizing time over budget, a low‑cost commercial library ($50–$300) remains the safer choice. For open‑source, education, or proof‑of‑concept projects, the free resources above are excellent. free hmi graphics library