Hi,
I just had a deeper look at my Plus H&T in order to wire it to a 5V power supply without using the USB-C connector on the side (I want the wires to invisibly enter from the back cover and the wall, not to see a wire and a connector on the side) and I was assuming there is no other way than soldering two small wires on the microscopic pins of the USB-C receptacle, but I had a very nice surprise !
As you can see from the attached images, the small PCB hosting the USB receptacle and the wake-up button is connected to the rest of the device by means of a 3-pins header: simply removing the PCB makes it very easy to connect the 5V and GND wires and also enables a third wire to control from far away (even by a Shelly 1 
) the wake-up contact.
Most probably I will be able to fit a 5V power supply module (taken from a very cheap USB charger) inside the batteries compartment and so entering the H&T directy with the mains supply.
Let's see if this will cause too much electrical or thermal "noise" to the sensor: if that will be the case I will take the power supply in the "upstream" wall box).
Ciao, Nicola.
).