I read a lot of these comments and people are thinking about traditional card games and electronic games of the past that are kinda sorta similar (but not really). They're missing the ONE HUGE ADVANTAGE of epaper displays: They don't need power.

It seems the big assumption everyone's making in the comments is that the displays will just stay there on the electronics box. The reality is that you can refresh the display and then take it back into your hand. You could even trade it with other players while disconnected.

Furthermore, these displays can be refreshed hundreds of thousands of times (some can do millions) and therefore can last a lot longer than regular cards. They're also stupidly cheap in bulk! Example of a cheap NFC-powered one: https://www.aliexpress.us/item/3256803070283516.html (not the best example since it's kinda thick but you can get much thinner ones around the same price).

You just need to come up with some example games that take advantage of the trading dynamic. Also, if you're up to the engineering it would be neat if you could use one epaper "card" to modify another one. Much like how in many card games you can add an "enchantment" or "modifier" style card on top of another to give it additional capabilities.

I also recommend adding a cover or shutter to the cards so that they can be refreshed without the other players seeing what it is. Once the card is back in your hand you can move the cover out of the way and see what you got. Alternatively, you could make it so that the cards refresh their displays upside down. That way you can refresh it without anyone seeing what's there.