I did in the same session apt update, upgrade and append a line for ma SDcard in /etc/fstab. Then sudo shutdown -r now. The phone never restarts, but the screen keeps showing the Furi logo. I then flashed following the instructions but App Exception! (PMT changed for the ROM; it must be downloaded. Please select "Format All + Download" scene and try again) (fw_throw_error,../../../flashtool/Flow/ErrString.cpp,27)) comboTimeout index(3) saved. I stay with the problem of the logo draining the battery. If I hold the start button, it stops… but comes back.
Trying again I get the message at the start of flash_tool: Application asked to unregister timer 0xc00001b which is not registered in this thread. Fix application.