Principal kubernetes consultant for a large firm here.
Kubernetes uses Docker runtime so that eliminates your first question. AWS also uses Kubernetes, EKS is a modified version of Kubernetes, and most major companies do not use things like Nomad because they lack the ecosystem tooling that something like Kubernetes has.
I think probably the best thing you could do to prevent issues like this is blue-green testing or proper integration testing with your infrastructure repository so you can roll back quickly when you realize that some change you made didn't work correctly. This is all in addition to significant amounts of it monitoring.
The site's down, and you raise a valid point. But:
Even starting from an ETA, there are improvements and variants that can be made. (For example, some Chinese clones of the 7750 added a safety mechanism to the date's quick adjust mechanism. It's a really simple and elegant design change, too.) The open source aspect of this project isn't just that there's a movement, but that there's a development process. Or that's what they say, anyway!
Also, pretty much every non-ETA/Sellita movement in the cheaper-than-Rolex market is just about marketing. The movement offers nothing of interest to buyers if it's just some tweaked CAD files of a 2892, because those buyers would just get an SW-300, which is the same thing [1] with better reliability.
[1] Or not the same thing; there are probably differences just like with the SW-200, but everybody in the market will think that way.
Kubernetes uses Docker runtime so that eliminates your first question. AWS also uses Kubernetes, EKS is a modified version of Kubernetes, and most major companies do not use things like Nomad because they lack the ecosystem tooling that something like Kubernetes has.
I think probably the best thing you could do to prevent issues like this is blue-green testing or proper integration testing with your infrastructure repository so you can roll back quickly when you realize that some change you made didn't work correctly. This is all in addition to significant amounts of it monitoring.