Well, I did something stupid and deleted the partitions as suggested in one topic. The phone won' t boot anymore, as expected, but no sign of getting it to flash the eMMC.

RescueOS worked and still works fine, tho.

How can I check for IO errors using dmesg? And is there some tutorial on how to flash the device using RescueOS?

Also, how can I return the partitions back to their normal size? And what partition table should I use?