Quick reply...

Are Other Halves stack-able? No, I think? The connectors would be wearing off pretty quickly, I fear...

Is e-ink screen Other Half possible at all? As in, would e-ink screen be recognised by OS as second display? I guess I should be asking Jolla if they plan to release a phone where first display is e-ink

It's just... Backcover for the sake of physical stability, and nothing else, seems to be such a lame use of space...

Another idea for electricity-using Other Half: combine TOHKBD with Light-emitting OH. Or would it be too bulky-and-fragile-and-expensive (and not-working), too?

Best wishes. Thank you.
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Per aspera ad astra...