"Envious of C++’s and Objective C’s credible claim to be the only languages that can seamlessly interoperate with C (due to header inclusion and compatible syntax)"
Wouldn't Nim and Zig also fit the bill?
The last time I looked at the Nim documentation, one had to manually declare C and C++ functions. I don't see how that's different from pretty much any other language that can call C (i.e. pretty much all of them). Then there's preprocessor macros.
I don't know how Zig does it, I'd have to look.
I expand on why dpp is the way it is in my DConf 2019 talk: https://www.youtube.com/watch?v=79COPHF3TnE&t=8s
Nim has an automated generator for C/C++ wrappers or translating from C.
Also there are very easy ways to create Python modules in Nim:
https://robert-mcdermott.gitlab.io/posts/speeding-up-python-...