The Olimex ESP32­-C3 module has a risc-v core, sure, but it's roughly equivalent to an ARM Cortex-M3.  The HW platforms targeted by Plan 9 and its tools are much more heavy weight.  I don't believe Plan 9 would be a good starting point for any ESP32-C3 development.  If the Olimex guys are looking for a monitor, then umon might be a good place to start.

     Ref: http://www.umonfw.com

The code is modular, clean, already supports about a dozen architectures, and should port to the ESP32-C3 without too much work.  And it shouldn't be difficult to add risc-v support to its built-in 'dis' disassembler.

Just my $0.02 ;)
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