Hey, Co-creator here. In regards to the first issue, we assume that you have applied Amazon's recommended bucket policy as per https://docs.aws.amazon.com/AmazonS3/latest/dev/WebsiteAcces.... We do this in case the website being deployed isn't meant to be publicly available.

Re custom frontmatter, with Jekyll we respect the defaults that are set in your config (https://jekyllrb.com/docs/configuration/#front-matter-defaul...). If a post matches a type or path that is specified in a default, we make those fields available in the post. We have come to realize that this feature of Jekyll isn't used as often as it should be (it's really useful) and are working on giving users the ability to add fields to their posts.