D1 is indeed the first mass-produced Linux-capable RISC-V SoC. SiFive made something like 500 HiFive Unleashed boards and probably 2000-3000 HiFive Unmatched.

D1 is indeed the first mass-produced Linux-capable RISC-V SoC. SiFive made something like 500 HiFive Unleashed boards and probably 2000-3000 HiFive Unmatched. They all used effectively prototype chips, made on MPW / Shuttle run. When the D1 came out I heard the initial production batch was 2 million chips. As with the SoCs that go into Raspberry Pis, the SBCs are a side-line.