Muse Pi Pro is a Raspberry Pi-sized RISC-V PC with M.2 and mPCIe sockets

The OrangePi RV2 is a less expensive RISC-V SBC option if you don't need 16 GB RAM: http://www.orangepi.org/html/hardWare/computerAndMicrocontro...

It also has two Ethernet interfaces and a full-size (2280) M2 PCIe slot for SSDs in addition to a 2230 slot.