This project of mine is similar to what you described with a power down mode. The power down and wake up can be automated. I'm looking to build a small business around such projects. Not sure how viable it is.
I made some stuff of mine for that display too, but the easiest way is to just use TRMNL's firmware, as it supports autoupdates and a few other nice features.
Here's mine:
https://www.stavros.io/posts/making-a-trmnl-device/
Plus this:
https://www.stavros.io/posts/making-the-timeframe/
And a few more things I never wrote about.
The Kindle project is just because I have a few Kindles lying around, so I might as well use them!
I should post that build too, with some photos, I really like it.