I almost bought an xteink the other week but held off due to lack of a frontlight option.
I instead resurrected my nook simple touch (2011) with this project [1] from XDA forums, its made it infinitely more usable and still has good battery life.
[1] https://xdaforums.com/t/nst-g-the-phoenix-project.4673934/
Thanks for mentioning both of these, the xteink and the nook resurrection. My old nooks are all slimy with the black material liquifying, and unusable just for that, else I'd pursue the XDA option. Looking into the xteink now, else Kobo. The one the post is about seems extremely appealing, but the price is a bit high for me, and the lifePo option makes the lesser one seem even more expensive. I really love e-ink. I could easily go with it for all compute.
5k cycles would be nice.