Can I piggyback and ask how people keep track of deployed software? Like if I have 50 products deployed some of which haven't been touched in 10 years and I want to be able to ramp up a developer to fix a bug on any of them?
In the medical device industry you keep what's called a device history file which tracks the configuration of each device you've sold by serial number. This DHF is meticulously updated whenever something is changed. If someone reports an issue this is information you can use to scope your initial reproduction.