X399 taichi just completely shut down

I think something similar, or even same thing, happened to my PC today.

So, I was just doing rather non-heavy workload (like watching Youtube) and suddenly my PC just shut down, like it lost power (but there was no power outage anywhere in my appartment, all other devices, even those connected to the same wall outlet were fine and worked uninterrupted). After that, it simply would not boot at all. I've noticed that after reconnecting the power cable, the LED underneath the "cog" on the board would first light up with an orange / red color for a few seconds, then turn blue and start flashing like I think it normally did before. I've tried powering up using chassis button, on-board power button, resetting CMOS, and... nothing.

So far I was able to verify that the connected drives, GPU and even PSU are fine, so the only two things left are either broken CPU, or (more likely), dead motherboard. Today is almost 3 years since I've bought that board, and I was definitely not expecting it to die like that, if it's a dead motherboard indeed.