Comment # 1 on bug 1059935 from Richard Brown

The installation media is active on all current SLE products (12 and 15)

https://openqa.suse.de/tests/1283245#step/zypper_lr/3

Refresh is disabled, but the media itself is enabled.

as far as I'm able to find, all SUSE & openSUSE products currently follow this
behaviour, and I can find no example in YaST on how to control it

However, I totally get why we might want the installation media disabled, shall
I investigate a way of doing that across the board?