Kind of related, the Ticwatch 3 uses an lcd screen on top of an OLED screen. So the lcd screen can last up to a couple weeks for just the clock, and OLED for a day or two for smartwatch apps.

I was interested in the possibility of using e ink in the same way, as a secondary screen combined with oled. Unfortunately I'm not an expert and could only find forum posts like this referencing an old screen made by a company that no longer exists, Pixel Qi https://electronics.stackexchange.com/questions/594549/oled-or-other-screens-combined-with-e-ink

And a 10 year old patent filed by apple https://arstechnica.com/gadgets/2011/04/apple-exploring-hybrid-e-inklcd-display-for-idevices/