Key eink patents are expired since c. 2017. But they bought potential competitors and keep innovating (and patenting), so the monopoly stays strong. If someone entered the market right now, with 2000 eink tech, and pricing at very low margin prices, they will go bankrupt: would you buy a 20" screen, no touch, ~70 ppp, refresh around 2 seconds for maybe $300? Also, patents might have expired, but key tech, such as precise micro-sphere manufacturing, is not under patent protection, but under trade secrecy: on top of old tech, it would be unreliable. Some like Zhiwei specialize in epaper for tags using old tech, but only for b2b and barely below Eink prices.

Competition explores completely different technologies: Daylight DC-1, Reinkstone, ChLCD e.g. from Iris... but either the tech isn't good enough to generalize or be cheap (the later), or the niche economics don't allow the inventors to keep investing (the two first).