From a software-complexity standpoint, something like 64 MiB of RAM possibly even 32 MiB for a single-tasking system seems sufficient.
Projects such as PC/GEOS show that a full GUI OS written largely in assembly can live comfortably within just a few MiB:
https://github.com/bluewaysw/pcgeos
At this point, re-targeting the stack to RISC-V is mostly an engineering effort rather than a research problem - small AI coding assistants could likely handle much of the porting work over a few months.
From a software-complexity standpoint, something like 64 MiB of RAM possibly even 32 MiB for a single-tasking system seems sufficient.
Projects such as PC/GEOS show that a full GUI OS written largely in assembly can live comfortably within just a few MiB: https://github.com/bluewaysw/pcgeos
At this point, re-targeting the stack to RISC-V is mostly an engineering effort rather than a research problem - small AI coding assistants could likely handle much of the porting work over a few months.