With the charger plugged in: hold Volume Up + Power for about 15-20 seconds until you see any flicker, release, wait 10 seconds, then press Power alone to boot normally. This clears a hung EC (embedded controller) state, which is a known cause of blank-screen boot loops on Surface Laptops after an unexpected shutdown.
While attempting to boot, connect it to an external monitor via USB-C. If the external display shows Windows booting normally while the internal panel stays blank, this points to the internal display cable or panel rather than the motherboard — which matters for whether this is repairable or a warranty/paid-repair case.