It just rooted back to my frustration when I was trying to fill in missing implementation details on projects like Skia (at the time it lacked support for Vulkan.) My very fundamental core belief is that for core libraries like say, Skia, Neural Net Framework, and other crucial projects like that should offer a way in C API that allows every type and implementation to be extended upon by any other language that can interface with C API by providing your own VTable or whatnot.
One of the approach I do for my GUI Toolkit written in C (specifically on Linux to replace QT and GTK) was making a single inheritance object oriented programming in C.and if you insert the base class type structure at the top of your custom struct type and provide your own VTable for those objects, you can readily extend the underlying library natively in whatever programming language you use assuming it can talks to C API in a complete sense.
Let me know if you want a demonstration of this, I would be happy to find the time to set up a small sample to give you the idea on how it's done.
And I am also aware of the criticisms on those approach, verbosity of attempting to implement object oriented programming in C is kind of absurd and the API coverage would balloon. That is largely why I work on a Compiler-Generator Framework specifically to address the challenges by allowing me to add dialects on top of C Language such as generic, object oriented programming, and various dialects. I brought C closer to C# in term of syntax and features and at the end of compilation, it still produces readable C language code output and it also generates what I called an FFI-JSON. It's essentially a JSON file that describes all of the types used in a C project, the sizes of integers/floating points, structure types and it's fields/offsets/sizes comments, and function declarations. It's done in a way that you could read the JSON file and generate your programming language binding library saving you weeks of work.
This is not the first time it happens with Dotnet Open Source packages, there are some pretty funky things going on namely:
Imagesharp (They re-license from Apache 2 to something like Community/Commercial licenses and threw a huge fit over it)
Fody (It expects the software contributors of Fody to be a patron.)