I'd love to get work done in sunny locations, like gardens. But these LCD screens make me squint. e-ink would be THE solution to this, but the e-ink displays are too expensive, to well supported and not very big.
But yes, it works as an external screen. Check out VNSee for this https://github.com/matteodelabre/vnsee
Maybe the rM1 might be the best choice for this. I'm not sure...
The rM2 is a lot trickier. A full reverse engineering of the drawing routines is still unfinished, as far as I know. So you either manipulate the memory of their closed source application or reuse big binary chunks of it. There are of course abstraction layers built over that by the community but as of today I believe it's much less refreshing than the rM1.
The rM1 used the chip electrophoretic display controller directly , while the rM2 has a software controller which is closed source. Hence much of the complications