A few days ago, my Satochip wallet arrived, so let me mention it here too.

Connected with Sparrow and Electrum—so far, it seems to be exactly what I was looking for.
I also tested it on a very old smart card reader, and there were no problems either. It would be good if Electrum had native support for the Satochip plugin in some future updates.

I also read your questions about the custom design. We are working on something not "crypto-related". Stay tuned.