I've only looked at the HashiCorp tools, not really used them. My understanding is they originated in a VM-based world (?), and I've worked almost exclusively with containers. I'm sure that has changed over time.

I will say that I looked at HCL and it looks very nice:

https://github.com/hashicorp/hcl

But somehow it's not as popular as a mess of YAML and Go Templates? That genuinely leaves me scratching my head. I guess it's because people pick platforms and not languages? (BTW, in 2009 I designed and implemented the template language that Go templates are based on, and I find their common application pretty bizarre, e.g. in some Helm charts I looked at from this thread)

Oil is growing a config dialect that looks a lot like HCL (although it's convergent evolution; I've never used it.) I think there is a lot of room for mixing declarative and imperative; as far as I can see HCL is mostly declarative (defining data structures).

Anyway I'd be interested in reading about HashiCorp stuff but for some reason in my neck of the woods I don't hear too much about it. Maybe that's because they're paid services and the open source Kubernetes seems attractive by comparison? Or is it more of a VM vs. container thing?