“E Ink” is a company, producing displays with a very specific proprietary technology. I think you mean to say more “e-paper”, which is a generic term for “paper-like” displays. And unfortunately, right now the only real competition is RLCD (reflective LCD), which is arguably non paper-like enough to qualify. Yes, it’s reflective, but other than that, it’s just a higher density Game Boy screen. Which is great and all, but it can’t compete with E Ink in a lot of aspects. It doesn’t have retention, you gotta power the screen, so no signage and stuff. It has LCD-grade bad viewing angles.

RLCDs are cool for certain uses though. For example, I sometimes choose to play on my AGS-001 over my Analogue Pocket if I’m outside in bright daylight.