WCH has launched some interesting RISC-V microcontrollers in the last year or so, including the “10 cents” CH32V003 RISC-V microcontroller with 2KB SRAM and 16KB flash or the CH32V307with more resources (up to 64KB SRAM and 256KB flash) and additional peripherals.
So far they were programmable in C language using MounRiver IDE or an open-source toolchain, but WCH has now announced Arduino support for many of those RISC-V microcontrollers which should enable more people to get involved.