Serenity’s time is mostly spent on Grove, our older and newer infrastructure (ie. Ansible-based vs Terraform based). The Grove documentation has its dedicated page (grove.opencraft.com), however, we have no additional sources for the infrastructure.
The new infrastructure is written in Terraform. All modules are documented in their respective readme, and we assign meaningful descriptions for (almost) every variable which is used. I hate to say things like this, but the terraform code is really self-documenting in this case. Also, there are bunch of comments where it is needed in the code. Like this comment.
The question is: What documentation are you interested in? We probably have answers for almost everything, but we have no giant knowledge base.