Help with strange keyboard problem
It sounds like your posture/orientation sensor is misreporting the device’s position. When a Surface thinks it’s folded back into tablet mode, it automatically disables the Type Cover + touchpad and if that sensor glitches, it’ll do it randomly. The upside-down screen + dead keyboard combo matches that exactly.
A few things you can try:
Full Surface Recovery Image reinstall
Not “Reset this PC,” but the official Surface Recovery Image from Microsoft. This rebuilds firmware + sensor calibration files, and it fixes a lot of weird sensor bugs.
Install the full driver bundle afterward
Grab the complete SP8 driver pack from Microsoft and install it after Windows finishes updating. This reinstalls the Sensor Fusion + Surface Integration drivers.
Sensor test in UEFI
Since it happens before Windows loads, gently tap/flex the upper-left area (where the magnetic hall sensor usually sits). If the screen rotates or the keyboard cuts out in UEFI, that confirms its hardware.
If it triggers in BIOS, it’s almost certainly hardware
At that point it’s usually:
A failing hall/orientation sensor or the sensor fusion board/cable.
Not a Type Cover issue.
Before paying CAD $900, definitely try the full recovery image + driver bundle. If the problem still shows in UEFI, unfortunately that points to 
HARDWARE.