The PineNote is perfect, except a dealbreaker is it is not colour e-ink. A microSD and HKS would be nice additions, but I’d buy one or more from any manufacturer with a Linux colour e-ink display. Looking for something like Remarkable, but a Librem 11e for example.
When my friend played around with e-ink displays a decade ago, it wasn’t a good state. Very few manufacturers, you essentially had to reverse engineer the display, and certainly colour was not widely available. Not sure how it is now, but probably not a walk in the park: E Ink Kaleido™ 3｜E Ink Brand｜E Ink Product
Market timing for such a product is good given the recent news about Kindles soon preventing you from using USB transfer, and Amazon editing already published books on your device to be more woke.