Boox Note Max. a4 size, expensive as hell ($650 I think), but it runs Android, can install stuff from the play store or side load apk. Ships with a very capable document reader can handle ebook formats, pdf and has good support for drawing and annotations.
Regretably, the Boox Note Max or Remarkable might be a better choice than any Fujitsu reader. I am on my second device from Fujitsu and I will not purchase another one.
Like the Sony DPT readers, the Quaderno is would be great product ... however,
1. there is no customer service in the EU/US markets. Something broke? Bin it.
2. the devices are quite fragile, with poor longevity.
3. the closed source software does not support modern systems such as Apple's M4 Macbook series.