I’ve noticed a lot of projects use riscv64 as shorthand for the rv64gc ISA, especially when it’s understood that there is an MMU, maybe an FPU, privilege levels, and any other extensions that a modern OS requires.
Anyway, I did find this on the Debian website[1]. So it seems they mean rv64gc.
[1] https://wiki.debian.org/RISC-V#Hardware_baseline_and_ABI_cho...