There's a few gotchas here. A lot of those color e-ink displays don't work like a LCD does, where you have R/G/B subpixels per pixel and get to mix final colors out of different intensities. Instead, a "7 color display" really means each pixel can only be one of 7 pixels.
Another gotcha is that in some implementations, the screen refresh will go color by color, so for multi-color content, the refresh time is quite long (as in, you don't have a pixel flipping to blue and another flipping to red concurrently).
This is just to manage expectations -- the result is still very cool.
https://www.waveshare.com/product/displays/e-paper/7.3inch-e...
Looks nice, but the full refresh time is like 30s.
[0]https://codeberg.org/Freeyourgadget/Gadgetbridge/wiki/Fossil...
I love e-ink in general, it's a shame that it's still so rarely used. My fossil hybrid hr watch uses it, for example, but though the watch itself is incredible, the app is pure garbage. If that weren't the case, I'd recommend it to everyone.
I wonder if there aren't a lot more cases like that, where it seems like costumers don't like the technology, even though they mainly resent the paired implementation of the big players who thought that the technology alone was enough of a selling point, and therefore neglected the software.