https://www.home-assistant.io/

They have customizable dashboards. What I'm really looking for is something I can use as a sort of command center in a few places in my house. It allows me to control the things I care about, shows my upcoming schedule, and whatever else is relevant. By my work desk, the #1 thing I care about is upcoming meetings. Other places, I care about other things.

Critically, though, I don't want it to glow. I want it either e-ink or purely reflective LCD.

This is probably a few devices. Ideally, there'd be small / cheap ones with mechanical switches and a tiny screen to replace my light switches, and big ones for my living room, work room, etc.

I think the trick would be to start with something, so one doesn't have an infinite engineering task, and so there are ready frameworks for modularity. Either Home Assistant or dash would be decent starting points, depending on which direction this took.

But yeah, now that I mention it, I have a vision in my head for what I want (which I would buy). Retrokludged features without the same vision would probably not get us there.

So I'll cut this back to what everyone else is saying: Calendar flexibility. This needs to sync with home, work, and other calendars, so at the very least, Outlook.