GRiSP runs on an RTOS using POSIX compatability. So baremetal-ish? Still you can apparently program RTOS tasks and control them from Erlang land. :-) Also Nerves supports the GRiSP board itself not the RTOS; pretty sure Nerves runs it using Linux IIRC.

Sorry, your nit might be wrong :) As elcritch covered the GRiSP case I'll just try to add some useful context.

Nerves stacks the BEAM on top of a small Buildroot Linux setup. The general rule I hear from the Nerves team is "if it runs Linux, it can run Nerves" which is mostly true.

I was considering whether Nerves could run on something like the ZSA Moonlander keyboard and then we run into a limitation of the BEAM apparently. Frank Hunleth of Nerves said the BEAM requires a device with an MMU. This is above my paygrade so I'll take his word for it ;)