How do I confirm the motherboard is dead?

My Pixel 3 was suddenly dead. At first, I thought it was a battery issue. Unluckily, there is no charging icons after battery replacement, no matter wired or wireless charging. I know it's less likely that both charging units malfunction at the same time. However, I've found that the motherboard seems to have response to wireless charging. My Pixel Stand 2 has charging response as well. The part marked in blue of the motherboard seems warmer than before charging.

How do I tell the motherboard is dead?