The nanoCH32V003 is a tiny development board featuring a general-purpose 32-bit RISC-V core. Some of the peripherals found on this low-power embedded device include up to 18GPIOs, 1x USART, 1x I2C, 1x SPI and it can be powered via USB-Type-C.
The nanoCH32V003 is a RISC-V dev board available for $1.50