The best e-ink tablet I've tested was not made by Amazon or ReMarkable

Review: The Onyx Boox Tab Ultra is possibly the highest-specced e-ink tablet on the market. For some, that could be overkill. For others, it's exactly what they've been waiting for.

source https://www.zdnet.com/article/onyx-boox-tab-ultra-review/#ftag=RSSbaffb68