What RISC-V extensions is this built for? There is a target triple of riscv64-unknown-linux-gnu listed so i assume the baseline RV64GC that the Linux kernel is built against.

It makes sense to be conservative with a new architecture but new high performance RISC-V cores such as from SiFive[1] are going to meet RVA23. That standard has vector and bit manipulation extensions that could be used to improve performance with a python interpreter. I guess more testing needs to be done to see if raising the bar is useful.

[1]https://www.sifive.com/cores/performance-p800