[camel-cdr]

> most devices on the market do not support the C extension

Name one that doesn't, it's exactly the opposite (for 64-bit).

[GeorgeTirebiter]

Maybe you've found the solution: RV32 must have the C extension.

RV64 and RV128 must NOT have the C extension.

Problem solved?

[camel-cdr]

No I meant, that for 64-bit CPUs virtually every available one supports the C extension.