Not able to dump flash as it is protected.
While messing with it - after toggling protection bit back and forth - my JL3 GRBL firmware is no longer booting. Yep, I’ve bricked it. Later found here:https://chowdera.com/2021/04/20210426103900089b.html
that flash will be erased on unlock, all Fs now. Exactly what happened.
Oh well, even more pressure to get recompiled version working.
At least I can confirm that hardware is wide open, that 4-pin header is STLink port and flashing with STLink is trivial. Just need new firmware.
Fun Sunday!
I will post when progress is made.