Help! My PC Died Suddenly While Gaming, Is It the Motherboard?

I was in the middle of gaming when my PC suddenly shut down. When I tried to power it back on, it would only start for a second before dying again. I've attempted a lot of troubleshooting: I've switched the power supply, tried a different CPU, tested with one RAM stick, did the CMOS battery reset, and even tried booting without the GPU. The only time it didn't shut down immediately was when I disconnected the CPU 4-pin from the motherboard. Given all this, do you think my motherboard is dead, or is there anything else I can attempt? Here are my specs: Ryzen 5 5700X3D, 16GB RAM, RX 9070 XT, and a Thermaltake Toughpower GF3 850W PSU.