Heads+Qubes: editing GRUB before boot

[apparatus]

"Maybe I messed up my qubes installation?" related support questions involving "some" Heads subtleties, aka "How to disable autostarting of service qubes at boot without Grub interface"

Here is another customer question that was addressed to me that should have been addressed to the forum for obvious reasons, being Qubes OS related: Sys-net stopped starting I checked pci devices and reset. After that it started to boot but it wasn’t searching for networks so I was unable to connect to the WiFi network I use. I thought that maybe it was missing a PCI device so I then checked and that didn’t work as I was unable to know which one to add or not. Some interesting bits here a…