ryguw, On Feb 1st, 2024, #Apple released Pkl. Pronounced "pickle", it is a complete configuration scripting language, including a JSON/YAML/XML/more compiler, a language server, bunch of IDE plugins, and of course direct bindings for your favorite programming language, for quick adoption. A #Python binding seems missing.
I like how a Pkl config's specs and values are colocated. Always hated maintaining separate schemas for very simple configs.