YAML is fine if you use a subset (don't use the advanced features - not like you know those anyway) and use explicit strings (always add " to strings), otherwise things may be cast when you did not intend values to be cast.
Example:
country: NO (Norway) will be cast to country: False, because it'll cast no (regardless from casing) to false, and yes to true.
country: "NO" should not be cast.

People are working on making S-Expressions a standard: https://datatracker.ietf.org/doc/draft-rivest-sexp/
Note: This is just a draft, but improvements have been happening since 2023.
I probably won't like the parentheses, but I think I'll take it over yaml/json/whateverelse.