So, I was building GCCs and the Pi stopped responding.
Then a bit later, the Ci20 stopped responding.
Inserted the Pi micro SD card into the laptop and it didn’t show up.
Interesting, right? looks a bit like maybe I’m breaking the flash by writing too much.
Turns out in the end – after a bit of experimenting and swapping parts and getting things working (the SD card showed up on the laptop after a laptop reboot) the culprit was…
*The ethernet cable used by the Pi board*.