Since the Nanno Every can only accept 7v - 21v in the Vin input and I do want to use the power regulator on the board, it is possible to feed the 5v directly to the USB input of the board and using this power regulator?
@eberendsen Connecting an external supply to either 5V or 3.3V pin will damage your board. Connecting to 5V pin will definitely damage the onboard MPM3610 DC-DC converter and connecting to 3.3V will damage AP2112 regulator. Arduino Nano Every is designed to only receive external input supply via VIN, else you damage your board. See https://content.arduino.cc/assets/NANOEveryV3.0_sch.pdf
Applying a weak 500mA USB power to the USB connector is no problem. The onboard 5V voltage regulator gets reverse current, but that is okay.
If you apply suddenly a very strong 5V to the USB connector, then the current peak can damage the board.
Using the 5V pin is more dangerous, because there is often no polyfuse and current can go into the computer (from the Arduino board via the USB cable into the computer). It depends on the board and the circuit. But it is mostly the same as with the USB power. If you apply a weak 5V to the 5V pin, then the voltage regulator can deal with the reverse current and the computer will probably not get damaged by the current into the USB bus.
Your Nano Every has a diode for the USB 5V. So the computer is safe, whatever you do.