The whole point of RISC-V is that there _is_ GCC support, since a decade, already. Even assuming they have proprietary extensions, it's pretty unlikely you nee

The whole point of RISC-V is that there _is_ GCC support, since a decade, already. Even assuming they have proprietary extensions, it's pretty unlikely you need them in application code. At worst it's just in setup code. However I didn't see any of the usual "bragging" about extensions, so I doubt it. Usually the biggest issue is lack of [good] documentation, but I suspect this will work itself out over time.