Sorry about this issue everyone.
This is indeed an incompatibility of the feature Build Config Validation with the beta version v2 of our deployment tooling dpl which is not used by default, yet. Build Config Validation applies a formal schema to your build configuration that specifies things as required for dpl v2, but not dpl v1 even though this is still the standard version (if everything goes to plan this default will be switched in Jan). This is an oversight on our part in coordinating these two non-trivial releases.
We are working on ways to reduce these issues. In the meantime you can resolve this by opting into v2 using:
deploy:
- provider: [name]
edge: true