Kobo Aura One or the new H2O Edition 2. It's a frontlight, not a backlight, but you specify eink so any lighting must be a frontlight. Both have temperature adjustment. Neither needs rooting in order to install patches, alternative reader software, etc. Neither, however, has page turn buttons. You can swipe or tap, with configurable tap zones.
I very strongly suggest abandoning reading .mobi files, though. It is trivial to convert them to epub or kepub, which perform far better.
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