> Usually non-technical persons do not give a faint fart about ‘major’ ‘version numbers’.

This type of user is actually usually, IME, easier to explain it to:

“It’s a different platform and our software will not work without changes”. The less they “give a faint fart” about details, the easy it is to tell them the effects and have them accept and move on.

At most, you might occasionally need to invoke a car analogy: it’s like trying to use accessories designed for an older model year, when there has been a design change between model years – some things just don’t fit right anymore.