The folks over at XDA have rooted the original Hibreak and are actively working on trying to reverse engineer the display drivers so they can install LineageOS. The person working on it right now has a good track record with other e-ink phones.

I wouldn’t pull any triggers until it’s released, but worth watching that activity.

ETA: https://xdaforums.com/t/bigme-hibreak-root-mediatek-6765.4697830/page-7

I know it’s not a direct answer to your question, but I just wanted to draw attention to the IKEA Starkvind air purifier, fully compatible with ZigBee, totally offline

Some days I don’t wet the bed, how will it recognize my presence without a steady stream of moisture?