A bit late to the thread but it is still on the front page. I've got some esp32 risc-v eval boards I've meant to mess with, but I'm nervous about their availability due to political instability and also while the rust support seems pretty great, I don't really know what is going on down in the hal and whatnot. Is rust on the 2040 well supported? Is it too well supported? Is it well enough documented that I could start with no software of any sort and load a pure rust blob and have it do some uart or something? My motivation is to recapture the feel of the c64 or Amiga1k wherebthe only mmu is optional page protection at most and you know what everything in memory is doing.
If I get your question right, you still need some host software (like a rust compiler)! It's not exactly micropython experience.
The bare minimum would be one of the examples [1] compiled with a Rust compiler and then transformed into a .uf2 file with elf2uf2 [2]. You can then just drag and drop the .uf2 file into the "mass storage device" presented by the bootloader. To get the bootloader to mount, you press a button on a Raspberry Pico (or short two outputs if you're using bare RP2040) while plugging it in.
You'll probably want a debug probe [3] driven by probe-rs [4] at some point, it's just much more convenient to flash and debug with it.
