E-Ink for Productivity: An Introduction

There are certainly some e-ink devices that are able to do this, the TechnologyConnections fellow did a couple of videos that cover it, amongst other things: ▶ this video & link Though he is using a Boox product and I'm wary of them over the GPL violation thing: as well as the general “they'd piss & moan and send the lawyers round if someone took their stuff and used it unlicensed” hypocrisy, the paranoid cynic in me thinks there is something they want to hide in their customisations (hooks for calling home or some such). Also, those clips are a few years old now so some of the problems he was having may have been ironed out in newer devices & software updates. Another option is running a VMC client on any tablet that isn't walled off so that you can't: there are a number of VNC servers that create a hidden virtual screen and mirror that so the connecting client because the extra screen.

Alec of the YouTube channel Technology Connections has a video[1] about his experience with an E-Ink device on his second channel. He wanted to see if this would improve his productivity, so it's not exactly the same as your question, but it's still worth a watch, imho. [1]: ▶ this video

Alec of the YouTube channel Technology Connections has a video[1] on his second channel that you might find interesting. He demonstrates how one can use modern E-Ink displays for basic Internet browsing and such. [1]: ▶ this video

About a year ago Technology Connections on youtube tried to use an eink display and thoroughly described his experiences. * E-Ink on Android, and other new things! link * E-Ink for Productivity: An Introduction ▶ this video

Take a look at the Onyx Boox Max series: link They're 13.3" displays, work with Android and you can use them as an external HDMI display. However, the refresh rate is still poor, not nearly 20-30Hz. The Technology Connections Youtube channel has made two very interesting videos, showing the many caveats of the device (it's an older model, but I'd guess most of it still applies). The main issues are poor software and slow CPU: ▶ this video

If you two are serious about this, you'll defintely want to check out Technology Connections' series on e-ink: (quick intro): link (starting the breakdown): ▶ this video He talks about that exact concept and moves on to do real-world testing and setup of a very specific tablet usable as an external display. It's exactly as you say: Hacky and unpolished. But I found it extremely informative.

the Technology Connections yt channel has an experience report about the Onyx Boox Max 2 tablet (13.3 inch): ▶ this video tldw: it's not great for non-ereader tasks. the display is fine, but the tablet is hampered by slow hardware and bugs in its customized Android. using normal apps is challenging even with the compat tricks the OS gives you (e.g. disabling animations, "high contrast") he mentions that Onyx also offers a non-tablet e-ink monitor, maybe that's better?

Technology Connections (amazing Youtube channel btw!) has a few videos on using an Onyx Boox Max as a 2nd monitor: link (Intro) ▶ this video (2nd channel longer look, mini review) link (6 months later, tips / tweaks / long term review)