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There are but OP doesn't appear to be using e-ink, it's much too fast to be that. I would guess it's an unorthodox form of LCD display.

It’s reflective LCD (RLCD).

But with a backlight, which is novel I think?

Reflective LCD with backlight is called "transflective LCD" and they have been in use for years: https://newhavendisplay.com/blog/transmissive-vs-reflective-...

Ohh neat. Like the Playdate

Yeah the Playdate screen is lovely, but pretty rough without a backlight.