I admit that Nomad is a fair middle ground due to its clean DSL and also because of the homogeneity of their workloads.

The team at OpenAI used the k8s api to make extensions around multi-tenancy (across teams) to saturate available allocations, task specific scheduling modifications which were not supported by the k8s scheduler.

I don't know if Nomad has this extensibility. Their plugins were around device plugins and tasks when I last looked at it.