Mikey Sklar's BUBBY uses seven keys with chording patterns for input. The display makes for an excellent stand-alone training experience. It can be used as a USB HID keyboard or storage drive.
I recently built some prototypes for the pocket keyboard contest. One of the five, my "bubby", has been a pleasure to build and use. Full write up on the github page. With lots of pics – Mikey.
As of the naming: "Bubby" is an affectionate nickname for a friend, peer or even grandmother (Yiddish). This pocket keyboard, acting as a digital everyday carry device, is the friend that accompanies you.
Specs
7 keys
Form factor: 80 x 46 x 12mm – "thinner than a deck of cards in all dimensions"
ESP32-S3 + CircuitPython
display
note taking - save to flash, view as USB drive
Also works with Feather RP2040 (minus display code)