Apparently there are multiple crates but no official toolchain so unsure how that works in practice. You’re still limited to either waiting for hours or cross-compiling though since currently the best available RISC-V CPU is quad-core 2.5 GHz (which still looks hella promising, 2 years ago best we had was 1.5 GHz dual-core). This blog post by Drew DeVault goes into detail of how daily driving RISC-V looked like 2 years ago. I suppose these days it looks noticeably better, especially since Samsung and Apple have been eyeing RISC-V adoption due to ARM consortium doing some monopolistic shit with their licensing. But eventually, so far, not enough critical mass was attained and afaik the whole drama mellowed out a bit.

Regarding the energy efficiency, some experimental units managed to even be manifold better at this:

https://arstechnica.com/gadgets/2020/12/new-risc-v-cpu-claims-recordbreaking-performance-per-watt/

But on the other hand, studies involving some RISC-V models show quite the contrary when it comes to energy efficiency, although the thermal performance is much better:

https://link.springer.com/article/10.1007/s11227-024-05946-9

And below is a screenshot from a comparison by Gary Explains using more microcontroller models. So it really depends on the specific model, but it seems like the design of RISC-V has some solid potential to beat ARM in terms of energy and thermal efficiency.