The M218B worked, really?
I wonder now if you can get jetBook --> M218B --> Libre.
Note that, yes, two flashes are needed (no point in even trying after the first flash, just flash again).
Here's the link to the Chinese firmware directory:
http://218.240.9.39/soft
And the link to B v. 44:
http://218.240.9.39/soft/M218B044firmware.rar
Though it appears B v. 47 is the newest now.
I'll have to try this soon.
Note: I only tried M218A++27 in the past. The Chinese firmware was fine, but the Libre firmware still didn't work.