What do you mean? I have an Onyx BOOX MAX 2 PRO 13.3" and it works quite well. As a large-screen (close to A4) hi-res (2220×1650) e-reader it is very good, especially for scientific/technical papers. In addition to two-finger touch it has a very good Wacom digitizer with stylus. On the software side it has Android with Google Play and a lot of third-party apps work OK. Sideloading APKs is possible if e.g. you want to deploy your own apps. Where Onyx botched it is the external monitor feature: The device has an HDMI input port but the interface HW doesn't support the full physical resolution of the e-ink screen which is really annoying. But otherwise not a bad device at all - and most of what it leaves to be desired on the SW side can be corrected by installing suitable apps.
>A rooted Kobo H2O with koreader in landscape mode is vastly better
What would be the interface for using it as external display? or are you telling about using it just as a document reader?; in that case it might not even serve OP's needs.
The BOOX MAX 2 sadly doees not expose its full native resolution through the external monitor interface which is a real shame. Worse, none of the supported resolutions are integer fractions of the native resolution so scaling artifacts are unavoidable. It doesn`t even seem possible to sacrifice some border area and use a suitably-sized subwindow of the screen (e.g. FHD 1920x1080) without scaling. (If somebody knows better, please leave a comment)
Onyx pretends there is no problem and cheerfully tells frustrated users to adjust their OS theme and font sizes, over and over again [1]. Shame on them for ruining what could have been a great and unique feature. because wouldn`t it be for this problem, the MAX2 would finally be a decent sunlight-ready external laptop screen, at least for text writing and some light coding.
Well perhaps the problem is solved in the new MAX3 device.
Reg feedback for Onyx, you can try passing it to this YouTuber; he covers electronic shows world over and seems to have good relations with Onyx - https://mobile.twitter.com/charbax.
Sony is apparently still selling the DPT-RP1, and it still doesn't connect to Linux or read DjVu. I guess at least it has an OSX client.