TL;DW: turns out e-paper has become so good that a 1bpp image can be drawn, whithout ghosting or flashing, at 1/60 s. However, the controllers these displays ship with don’t have the memory bandwidth like TFTs to enable this… until now thanks to an FPGA wizard. His monitor is a direct LCD replacement and can switch between high-quality (greyscale/high-color), fast (dithered black/color dots) and power-saving (like low-bandwidth controllers nowadays) modes automatically based on content and user preferences. Everything is open source with off-the-shelf panel and FPGA. The project is finished and is accepting preorders.
Consider watching despite this “spoiler”, it’s very cool.
Einks usually degrade at fast refresh rates (or too many or too few reflashes), but that might be just the cheap ones (otherwise this product wouldn’t last more than a few years, which hopefully ofc isn’t the case).
But the “brightness” limitation of colour einks still bothers me a lot, the contrast on/of white backgrounds is just too good on monochrome versions (eg for books I don’t want colour einks), and it’s not just something I would only notice in direct comparison, it’s a constant feature/luxury.