I felt there were benefits in being able to accommodate a 13" ePaper display. This is because those displays are pretty analogous to A4 paper size, which is why they are used in big notepad devices.
I do have reMarkable which uses the 10.3" display, this is a common size now and, I must concede, probably quite adequate for the sort of tasks that can be performed on a black and white e-paper display.
What would you use for connecting the E-ink display?
The parallel displays use 8bit data + some clock and other extra signals, that’s a lot of IO required. Also a few special voltages are needed that are not available in the Reform so the adapter board is likely needed. It has ESP32 chip on it so it can communicate over a number of interfaces like i2c, SPI, uart, usb2, wifi.
Bit-banging SPI over the eDP data pins does not sound appealing, there is no GPIO connector, the ESP32 on the adapter cannot decode USB3 (3 only, not 2-compat) which happens to be available on a connector but nothing else I am aware of. Connecting an internal display over WiFi would be quite ‘special’.
One could use a DSI to RGB converter such as ICN6211 and go from there, with an FPGA or specialized epaper driver chip.
El Chipone, Al Capone’s chibi brother?
The thing is that ESP32 is not designed to drive an e-paper display and it clearly can. So with enough GPIO pins it’s possible to push the data to an e-paper display. The problem is getting the data out of the Reform SoC with very limited IO. eDP is likely too tied to the display subsystem and would not send arbitrary data. Not sure how well DSI is separated from the rest of the display subsystem on the SoC side, something to look into I suppose.
The demos of this seem impressive. Modos Paper Monitor Status Update
I had an idea sparked from a different forum. I think the idea of an e-ink screen placed on the reverse of the lid, where the logo would normally be present could be an awesome feature for one of the Reforms. Could display anything, and if it’s possible for it to update / render to it while still using low power (while closed), that could be awesome.
As hex pointed out the modos paper monitor is probably the absolutely best bet we have for an epaper monitor for our reforms that aligns with the values of the mnt reform project. It’s amazingly opensource from the hardware down to the gateware for the board!!! I had the pleasure of talking to some of the modos team at Crowd Supply’s Teardown even the past weekend and was very excited to share the project. Both MNT and the modos team are definitely aware of a sort of synergy between the projects but are both respectively very small and have much to focus on their own rights.
If you’re interested i suggest subscribing to the project for updates and maybe buying a board when the campaign launches!
The biggest draw back so far is the closest to size display it seems tested and easily available is a 13.3 inch whose panel is 285.8 mm x 213.65 outline which is a decent amount bigger in the vertical length. I need to dig into my reform to see what overall size we’re working with but it could still possible to make a monitor that uses the hinges but may be oversized for the base.
I also got a chance to talk to them this weekend. I brought up this 12 inch 16:10 display and they said that its been tested and works but not at full speed since it is above 1080p resolution. I did not get more elaboration of what that means. The Modus board apparently uses DP 1.0 which has issues with higher resolutions.
Anyway the Modus was seriously impressive and I will probably order one and just prop it up in front of the reform display when I want e-ink and use the reform normally when I don’t.
This 10.8 inch 1080p screen might be a better choice at the moment, but you would be losing a lot of screen real estate. I did not ask about it though.
I think no matter the choice a new bezzle will need to be made to support the screen.
I’m thinking of using a 6’’ e-ink kaldieo one + modos board for my mnT1000 remix project. I’ve been trying to decide on displays for that project and this might be a great opportunity for it.
Can confirm Pocket Reform would fit the 6-inch 60Hz displays that Modos is selling with its Crowd Supply campaign… 
Physically or electronically? Because a Pocket Reform with an e-paper display sure would be interesting!