My solution is tied to Home Assistant, which is running for the whole house 24/7 anyway, then, a Z-Wave smart plug to turn the PC on/off, and, finally, an EnOce

My solution is tied to Home Assistant, which is running for the whole house 24/7 anyway, then, a Z-Wave smart plug to turn the PC on/off, and, finally, an EnOcean kinetic battery-less switch to toggle it on and off. While we're at it, Home Assistant also powers on/off the TV, sets the input, sets volume, and dims the living room lights.