Roger
It
seems to me that the solution is to replace all the OpenSUSE
repos with a private repo you control that all your customers
use. That way all stay on the same version.
I had considered mirroring the repos locally, and only do that when I want, and only allow customer updates when we are happy with the repos, and the system updates are against those. If I did that, I would be very tempted to do it for Tumbleweed. We use 20 or so repos. I suspect that we could lower that list. It's things like NVIDIA (we do CUDA feature detection with YOLO), Intel IPP, and a few other non-SUSE things that may perhaps make things complicated.
The difficult part is maintaining our off-line thing. Many organizations really dislike and often will not allow what they see as rogue systems to connect to their network. Although the systems are highly networked, that is all inside the vehicle. We have purposely limited external connections precisely so they cannot mess them up. The expense when a system has been borked is rather high.