Rpi4 + Mesa 7C80: how to power-off?

Hi, the Mesa 7c80 board is a host for the Rpi 4B.  Looks like: desertshedstudio.com/wp-content/uploads/2023/01/7C80_RPI4_1.jpg   So supplying DC to the 7c80 (orange terminals) powers up the Rpi.  Which means that as soon as power is applied, it starts booting.

Then when Debian is shut down, the 7c80 has no way to unpower the Rpi, so it stays running.

We can control machine "on" power easily from a seal-in relay.  But has anyone devised a way to shut down the 7c80 automatically when Debian terminates?

I have mine set up using 1 of 2 ways, both are setting in the RPi

1, using the BOOT pin on button, this way you can turn off RPi IO power and still boot from halt using a button

2. Boot using the one IO pin on the header, and boot with button

the 7C8x is still powered at 5v