eInk is like a piece of paper, which gets MORE visible in the sun, but standard touchscreen LCDs/OLEDs get harder to see. I am not sure about the physics/reasons for this. Phones also aggressively dim screens to conserve energy and lower temperatures. Phones absorb a lot of sunlight, so a white eInk display is brilliant in that regard.
Refresh rate is a solved problem for eInk as well, but it comes with energy tradeoffs and... might still be proprietary. But 60-120 fps eInk exists AFAIK.
Transflective LCDs, which most bike computers use, are also reflective but have better contrast than eink making them more visible in sunlight. They are different than phones.
Trying to outbright the sun on a battery-powered device is an approach I've always found questionable.
E-ink, instead just lets the sun reflect off of it, does want some sort of light in the dark, but, perfectly visible in full-bright/direct sunlight.