The HyperPixel 2r from Pimoroni is a round 2.1” IPS capacitive touchscreen with high-speed DPI interface. Like its square and rectangular HyperPixel 4 brothers, the '2r' is intended for Raspberry Pi. Actually, the size is optimized for the Raspberry Pi Zero and Zero 2 W but, as it has the standard 40-pin HAT connector, it can be plugged on any Raspberry Pi equipped with such a connector as long as you are careful about the mechanical side of things.

The display’s resolution is 480 by 480 pixels without the corners. It has 18-bit color depth, meaning that it can display 262,144 colors. It supports up to 60 frames per second (FPS). The viewing area has a 2.1” diameter (53.3 mm) and a viewing angle of 175°. Its full diameter is 72 mm. With a Pi Zero attached the total height (or depth, whatever you prefer) is 17 mm.

This video shows what it looks like and what you can do with it.
 

Resources

HyperPixel2r driver
HyperPixel2r Python3 library
Source code from this video